Pet your Chao, evenly, with characters from the Dark and Hero storyline. When your Chao is close to evolving, it should be blue. If your Chao is not blue, but white, pet it with Dark characters, until it becomes blue. If you Chao is black, then pet it with Hero characters, until it turns blue. This does not work after evolution. If using a special Chao (Advanced, Colored, etc.) your Chao's color may not be black, blue, or white.
Pet your Chao with either Sonic, Tails, or Knuckles, excessively. When your Chao is close to evolving, it should be white. If your Chao is not white, pet it with Sonic, Tails, or Knuckles, until it is. This does not work after evolution. If using a special Chao (Advanced, Colored, etc.) your Chao's color may not be white.
Pet your Chao with either Shadow, Eggman, or Rouge, excessively. When your Chao is close to evolving, it should be black. If your Chao is not black, continue petting it with Shadow, Rouge, or Eggman, until it is. This does not work after evolution. If using a special Chao (Advanced, Colored, etc.) your Chao's color may be something other than black.
To make your Chao a Ghost, give it many Bats. Its legs will disappear and it will float.
To make your Chao wear something on its head (other than fruit), give it many Skeleton Dogs. Afterward, give your Chao certain items, and it will do the rest. To set your Chao's floating ball aflame, give it many Half-Fishes. Its floating ball will turn into a blue flame.
Raise a Chao either Dark, Hero, or Neutral alliance. Before evolution, raise that Chao in only one attribute (Swimming, Flying, Running, or Power), so that that one attribute is much higher than the others - recommended that attribute is on level ten, while the others are from one to five. When it evolves, it will be an "Advanced" Chao! The name of your Advanced Chao is formated as follows:
[Alliance] [Attribute] Chao
Examples: Dark Flying Chao, Hero Power Chao, or Neutral Running Chao
Raise an Advanced Chao, then continue raising it in one attribute, while barely raising the other attributes. Try not to raise the other stats past level seven. Your Chao won't evolve, again, but will just change appearance. The name of your Advanced+ Chao is formatted as follows:
[Alliance] [Pre-Evolution Attribute]+[Post-Evolution Attribute]
Chao Examples: Dark Flying+Power Chao, Hero Power+Swimming Chao, or Neutral Running+Running Chao
After your Chao has reincarnated for it's second time, give it one of every animal. It is highly recommended to choose a specific alliance (Dark = "Ultimate Devil" Chao, Hero = "Ultimate Hero", or Neutral), because the appearance of the Chaos Chao dramatically differ.
Full Egg Chao:
After a Chao's first reincarnation, give it a Skeleton Dog and an egg shell of the color you want the full egg to be. On it's second reincarnation, it will be a Full Egg Chao!
Raise a Transparent Chao and buy/raise/breed whatever color of Chao you want the Translucent Chao to be*. Once both Chao have evolved, give them a Heart Fruit and breed to get an Egg. When it hatches, it will be a Translucent Chao!
* You can have Advanced Translucent Chao, New Species Translucent Chao, etc.
Buy a Jewel Egg (anything but Gold or Silver) from the Chao Store on Sonic Advance. Buy a Shiny Lime Green Egg from the Black Market on Sonic Adventure 2: Battle. Once they have both evolved, give them both a Heart Fruit and breed to get an Egg. When it hatches, it will be a Transparent Chao!