Just got a T2i a week ago, my first DSLR. Was torn between this and the 60D but at a $300-400 price difference, I figured I can save that money for tuition and upgrade in the long run if need be. Fortunately, I don't feel like I'll need to upgrade anytime soon.
1. I know everyone says to charge the battery off the bat but a word of advice: pop the battery in and shoot a few pictures just to make sure the camera is functioning properly. That way you know out of the box whether or not anything's wrong. You'll probably get carried away and keep shooting until you get a low batt signal, but that's okay. Try not to run Li-Ion batteries too low and if you want to store them, don't store at full charge. 40% charged is where it's at.
2. Read the manual. I suggest playing around with the camera first and trying to figure everything out (which you probably won't) then putting it down and reading the manual. If you read the manual before even touching the camera, unless you've got photographic memory (...pun intended?) you're going to forget where all the settings are located.
3. If you plan on shooting movies at all, get a Class 10 SDHC card. I think they say you can get away with a Class 6, but better safe than sorry. I accidentally picked up a Class 4 and it records about 20 seconds of 1080p video at 24 frames until the buffer overflows and it stops recording. Will be returning the card soon.
4. Register your camera with Canon.
5.
http://photography-on-the.net/forum/showthread.php?t=847939 < Good thread for inspiration.
6. Have fun.