How to get into Warframe if you're having trouble:

I did not write this guide but I did edit some points to make it more up-to-date. This is an amazing guide that actually helped me out a while back and now I have 800 hours on the game. Whatever floats ya'll's boats. Credit to JayGeeBee of Reddit.

Bruh...

I am no pro, and there might be some mistakes or clarification needed as I've sometimes been intentionally vague in order to not intimidate new players. Sometimes I am being very specific. For more experienced players, let me know if I've made a mistake or should clarify. Here are some tips I wished I had known before playing Warframe that greatly increase your enjoyment of a game I consider to be one of the best action games ever made. Seriously? Yes. Seriously. If you wish to put the time into understanding its deep nuances, Warframe can become an intensely satisfying obsession of the greatest degree a video game can reach.
Thanks very much to u/MrVuule for providing several corrections.
Before firing off a single bullet or magic trick, hit Options and pull up your menu.

Expand your FOV

Move the Slider all the way up in order to greatly expand what you see in your playing field. Your Warframe will appear smaller on your screen, but this is amazing for situational awareness, and I personally believe it is a necessity with how joyously chaotic this can get.

Melee Camera

You may find you are confused when hacking and slashing as the camera doesn't seem to cooperate how you'd wish. You can toggle this option for the camera to either Follow the direction you are currently facing, or Switch to the enemy you are currently attacking.

Adjust your HUD

You can move your HUD to the very edge of the screen in order to clear the screen of any intrusive graphics. You can also choose to remove some information from here, but I would advise against this if you are a beginner and wait until you have a better understanding of the game.

Everything in this game is Free!

Except most cosmetic upgrades. For instance, Helmet Blueprints can be found or crafted, but color palettes and other ornaments are usually bought with real cash. By searching the Warframe Wiki you can research where to find the resources necessary for crafting new gear. You never need to spend a single cent on this game in order to enjoy it! It is most certainly not Pay-to-Win.

What is Platinum?

As a beginner you should have received some Platinum. DO NOT waste this. Once it's spent, you'll need to use real money in order to get more of it. I would highly advise not using your Plat until you've played a long time and absolutely know why you're spending the money.
Typically, it's recommended to spend your Starting Plat on more Weapon or Warframe slots, but again, don't waste this until you are 100% certain of what you need.

What weapons should I start with?

The Braton is better than the MK-1 Braton. The Bo is better than the MK-1 Bo. Pretty much anything is better than the Starter Weapons, which are just that, Starters. They're like training wheels. As soon as your Starters are Level 30, sell them for credits and get new ones, but make sure you get them to Level 30 first as this helps with your overall Rank which I will explain later.
After maxing out your starters, purchase a new weapon which is available with in-game currency called Credits. Other weapons require finding/crafting. You earn Credits simply by completing missions or finding Credits in Lockers (chests, crates, or what have you). The Braton is one of the better first-purchase weapons, actually. You should probably grab it.

Why am I leveling up so slowly?

Your Mastery Rank is not your level. It is your Rank. You level up your Mastery by leveling anything. The more new weapons and Warframes you level up individually, the higher this goes. If you, for example, level a Primary Weapon (such as your MK-1 Braton) to Level 30, you will not gain anymore Mastery from this weapon even if you Forma it (which you shouldn't do with a Starter) or get a new weapon.
Your Warframe, Sentinel, and Weapons gain levels by using them. Simple as that. They also level up rather quickly, actually. You'll even Level gear that you simply have equipped in-game. The level cap for any item is 30, but you can theoretically enhance any gear well beyond this, which I'll explain later.

What is Mastery Rank then?

It is an overall Rank for you as a player across all weapons, gear, and Warframes you have leveled. The higher your Mastery Rank the more weapons and gear become available to you to use, purchase, or craft. Once you hit Mastery Rank 6 is when most of the great weapons will be available to you. Mastery Rank 8 is when you'll be able to use everything, however.

Alright, I should be at Mastery Rank 2, but nothing is happening now! What do I do?!

You must complete a Test, which is like a mini-game. The Test will become available to you by viewing your Mastery Rank after you have reached a current Maximum and confirming that you are ready for it. I think you simply hit X or something, but I have not reached a new Mastery Rank in Update 14 yet. It might have changed because of the massive new UI overhaul. Complete the Test (mini-game) and you are now a new Mastery Rank.

Hold on, wait. Go back. What is Forma?

A Forma is an item which allows you to alter or add a Polarity to your Mod Slots. What the hell did you just say to me? Personally, I would advise leaving the Forma out of your mind until you have experimented with a better variety of gear, and have gained a more cohesive understanding of what exactly you want out of a Weapon, Warframe, and your play style.
Using a Forma will also totally reset that particular item back to Level 0! With each new Forma (and Level reset) you can significantly cut the cost of Mods and build some mega bad ass Configurations for your Weapons and Warframes.

What are Mod Slots?

Pull up your Arsenal in Options while in your ship (the Liset) and select Upgrade. Each piece of gear has a set of Slots which can be filled with Mods (playing card looking things that you collect during battle) that greatly expand the versatility and abilities of a single weapon, Sentinel, or Warframe. The Number in the top right corner of the Mod indicates the points required to use it. For example, if your Braton is a Level 3, you will not be able to use a Mod that costs 6 (or any number greater than your current item level).

What's the funny symbol next to the Number?

That is called Polarity. Some weapons will have a Polarity indicated on a Slot when in the Upgrade system. These are effing awesome because matching a Mod Polarity to a Polarity Slot cuts the cost of that Mod in half allowing you to squeeze far more out of your Mods and Gear!
Conversely, if you mismatch a Polarity, that Mod will now cost you even more than its Point cost.

Fun tip:

If you have a lot of Mods and several Points to play with, but still are not sure what to do, move down (on the analog stick) past your Mod Slots while in the Upgrade system and select Auto-Install. Before doing this, you can save different Mod Configurations for any Weapon, Sentinel, or Warframe by moving up above your Mod Slots and selecting Config A, B, or C. So, switch over to Config B and experiment with Auto-Install.
Alternate Configs are typically going to be for more experienced players who wish to create more effective Mod Builds for varying Missions and Enemy types. For beginners, I would advise not worrying about this until you have a much better grasp of the game.
Remember, Auto-Install will wipe out any existing Mod arrangement and give you a basic one, attempting to use as many Points and Mods available as possible. You can give this a try and decide what you like and don't like and you are welcome to switch out anything you wish. Again, this isn't highly recommended or anything. It might simply be a nice tool for a beginner to use in order to see an example of what is possible.

What is all this other crap I'm collecting?

These are resources necessary for crafting gear. Some of it is more rare than others. You will also come across Blueprints and Parts. For example, crafting a new Loki Warframe will require a Blueprint for the Loki Helmet, Chassis, and Systems, as well as an Orokin Cell. You must first craft each of these parts separately. Each individual part will require a mix of all of this other crap you're collecting such as Neural Sensors and Polymer Bundles as well as Credits. Where to find these Resource Drops will be indicated beneath a Planet Node in your Navigation system at the front of your Ship (the Liset).

Awesome! I found a Tower I Void Key? Uh... what in the hell is that?

These give you access to the Orokin Void which is a unique set of challenges and levels which are generally more difficult than your typical Planet missions and therefore give you more exciting rewards. You can try out these missions as a beginner if you wish out of curiosity, because you will not lose your Void Key if you fail. The Void Key is only consumed upon success (Except for Tower Survival or Tower Defense Missions. You will lose the Key if you quit early or fail after reaching the 5 Minute/Wave mark.) Generally speaking, these missions are better played with friends because of their difficulty and increased rewards. If you invite a friend into your game, only one of you will need the Key.

Why is there so much repetition?

Each Planet will generally be host to a single Enemy set and one Map Variation (or tile set). Don't complain yet until you've beaten your first boss and have moved on to a new Planet. There are currently 12 Map Variations (and growing) not including the Liset, Tests, or Dojo. There are three main Races of enemies. For example the Grineer is the first Race you will encounter and contains 21 unique Enemy types alone.

What is the Dojo?

You can join or create your own Clan to begin designing your own uniquely decorated Dojo and researching rare Weapons and Gear. Creating your own Dojo, however, is a massive undertaking and isn't recommended unless you've played a very long time and have collected an epic butt-load of resources to pour into it. It will most likely be better for you to join a Clan with an existing Dojo. This will open up a whole new world of cool options for you and I generally don't recommend taking this on until you have a better grasp of the game or if a Clan is open to accepting new players.
There are many new things that will become available to you here, but the biggest thing is Trading. This can remove some of the grind and help you on your way to new Weapons and Warframes quicker.

How do I do sweet moves with my Melee Weapon?

You need to find a Stance Mod which not only gives you the ability to use crazy cool Combos, but also increases the max amount of Points available to you for Mods.

What are the Black Squares on the side of my Mods? How can I make my Mods better?

You will find that you are collecting multiples of the same Mod. In the Fusion system while in your Liset, you can select several unused or copies of Mods to Fuse together in order to Level them up. For example, while in the Fusion system, the first Mod you select is the one to be leveled up. So, you select Serration, which is a basic Damage enhancer. You can then select any other Mod to Fuse into it in order to level it up. However, selecting just any Mod will result in a very slow, tedious upgrade. By Fusing/matching the exact same Mod you will be rewarded with much bigger results in upgrading that Mod. With Serration again, the ideal Fusion would be to select other copies of Serration and Fuse them all together.
This is not always possible, though. A strong alternative is to Fuse Mods with matching Polarities. In our example, Serration has a Polarity called V (by players) because of its shape. If you do not have multiple copies of Serration, using other Mods with the same V Polarity will be a good alternative to leveling this Mod.
Remember, Fusing Mods not only costs Credits (the in-game currency), but you will also lose whatever Mods are Fused into the Mod you wish to upgrade.

What are the Alerts I'm seeing at the Navigation menu?

These are your friends! These missions can make a huge impact on your speed of progress. Often they will come with bonus Credit rewards, as well as Blueprints and Rare resources upon completion! Play these and play them often. Once they're gone, chances are you won't see that opportunity again for a while.

How do I go beyond Level 30?

For your Warframe you will need an Orokin Reactor. For Weapons you will need an Orokin Catalyst. These are selected in your Upgrade system once you have found, crafted, or purchased them. Check the Warframe Wiki for Drop locations. These can be used whenever you wish. For new Warframes, I immediately install a Reactor if I have one. This will permanently double your Points available at any given time depending on your Level. If you are a Level 1, you will have 2 Points available for Mods. If you are a Level 20, you will have 40 Points. Level 30? 60 Points. The same with Weapons.
True, you may not enjoy a new Weapon or Warframe right away and adding a Reactor or Catalyst might be a regretful decision. Personally, though, if I've put the time, effort, and resources into collecting all the parts for something, I'm going to make damn sure I get the Mastery from it and try to find something I love in it. For example, I always avoided Nekros, but I happened to have most of his parts collected already and said, "Why not? These resources are just collecting dust. I'll give him a go." Well, I didn't like him right away. I put a Reactor on him anyway and forced myself to experiment with him and Level him to 30. He's now become one of my favorite Frames.
Sometimes experimentation and just giving things a shot is what will greatly increase your enjoyment and learning experience of Warframe. I've made some decisions which at the time felt like a mistake, but after learning more about it and using whatever it was, most of the time I came out loving it.

Credit to JayBeeGee:

All written by this fantastic guy.

[☆Arisu Yuki-onna☆]

nice guide very detailed though... missing something its very text rich, readers wont read everything perhaps try shortening the text a bit? just a thought.

[󠀡󠀡󠀡󠀡󠀡󠀡󠀡󠀡Shinchai]

The summary says "credits to JayGeeBee" while the end credits say "credits to JayBeeGee" all the while I wondered what a "jaypeg" is

[brindaharesh]

Very well made and comprehensive! Perfect for a noob like me

[Talion]

Black Squares on the side of my Mods? - Abit outdated ;)

[Bluegills]

"bruh"
nice meme *tips fedora*

[CrixusAegis]

You don't have to spend real money to get more platinum, you can trade with other players for mods or rare parts for weapons or frames, for platinum, so technically everything in the game is free, just takes alot of grinding.

[Rocknrow]

I wish I found this when I started out, would've saved alot of time 11/10 would read again

[Magnificent Marios]

Nice guide , i am new in the game and it was a good start reading this guide !! TY

[twystd]

Very nice guide. Can't read it all rn although I wish I could. xD
If there isnt already, perhaps put a piece about the foundry?
10/10 would IGN again -bang

[Stand with Ukraine]

Well done.