Okay, most of the medals are pretty obvious. I've gotten all of them except for FRIENDLY FIRE and MASTER ACHIEVER.
I assume MASTER ACHIEVER is achieved by getting all the other medals.
KARMA ARMOR, CLASSIC GAMER, and THANKS FOR TWEETIN' can all be achieved by clicking buttons in the main menu.
MIND YOUR CODEC MOUSE is achieved by rolling your mouse over the camera while viewing a codec. Codecs are the dialogue levels in adventure mode. The camera is in the little triangle in between and just below the two screens.
OMG! AN ANAGRAM!? is achieved by watching the final OUTRO cinematic all the way to the end. I don't mean to where it says "The end," I mean to the end of the cinematic.
If anyone can tell us how to get the FRIENDLY FIRE medal that would be much appreciated. Based on the other two medals in that set, I have a feeling it has something to do with the INTRO, since the second medal is in between the INTRO and the OUTRO and the third medal is in the OUTRO, and they're both in non-gameplay places. But I could be wrong.
For the 99 bounce record, you have to play classic mode with hard difficulty. When all "lanes" are with 100%, it's very easy to beat the 99 bounces.
For 99 bounce you don't need hard mode, just do it on easy. 66 you can get before, then when your fuel becomes infinite then you can get 99, I got 166 that way. Don't try it on combo, cos its really hard!!!
Master achiever isn't shown that you have unlocked it but goto medals and you'll know. Wish there was more when you get it...