New to BL2, how should I handle the playthroughs?

[The Pilgrim]

When I played BL1, I tried to do all of the missions in one playthrough since I didn't know about the "playthrough 2-2.5" feature. I was left hugely overlevelled at the end which, well, sucked.

Now I'm starting BL2 and thought I'd do mostly main missions with some side stuff, but I'm already overlevelled (just reached Sancuary at lvl 9, story missions are recommended lvl 7 at this point).
Should I just rush through the main story and ignore everything else, then do everything in PT2? What about PT3? I'm kinda unsure when to do what (including DLCs, where do those go?)

Could you offer me some advice?

[trukr]

Look at you next story mission's level. If you think you can and want to, go for it. Maybe use side mission when you need a bit more level.

Try to finish the first one around level 30, the second one should be done and you in the third at level 50.

The second one scales everything to level 50 once you finish the story, if you are under level 50 this lets you do things not yet done for some level 50 gear to start the third one.

Be sure to enter the third one at level 50, if you start and level 47, it still scales to level 50. However, if you enter at level 61 it scales to level 61.. and there you are with all that level 50 and under gear getting destroyed.

[prpl_mage]

For your first run, avoid the dlc. They are pretty low but if you play through them then you will be way overpowered for the story.

Second run play up to Bloodshot ramparts and then give some of the dlc a go. Or something.

You also get experience from completing challenges, so if you do a lot of that then you'll get more levels as well.

[shoobie]

you will at least need to be the minimum level for story missions, otherwise you will have a bad time.

[Kriegisyourbae]

I'd actually recommend doing all the missions that somehow sound interesting, no matter if you are overleveled or not. I think for the very first playthrough you should mainly enjoy the story and missions as well as the humour of the game. Regardless, you should try to finish the second playthrough as fast as possible as you already know the whole story. Just do what is needed to finish it at around level 50. In the last playthrough everything scales with your level, so this is a good run to finish all the side missions left so that you experience the whole game. After that, start farming, start a new character or try to reach the overpower levels.