Wow...
Well, obviously you need to decide what kinda chassis you want.
Do you want to go scale (realistic) or not?
What transmission? Pede, Stealth, Emaxx, etc...
You could do a crawler with the monster truck style tube frame, or a straight railed truck with links or leaf springs, or a real style truck frame with the narrowed front, dropped center, and raisied front and rear. Then you need to know what axels your going to use. TXT, TLT, WK, Clod, etc, etc...so you'll know how the links (or leafs) and shocks will mount.
You can build a chassis out of many materials. Steel, aluminum, brass, lexan, carbon fiber, and if you want to get really out there, wood. You could utilize already existing parts. I saw a little 2.2 crawler with a chassis made out of a couple 1/8 nitro buggy shock towers.
Otherwise, just look around the board. Ive only been here a few days and can already tell you that the answer to your question is literally on nearly every page. Pull out a piece of paper and draw out some ideas.
-Chris