Step 1: Materials and first step
A cage trap with plate-trigger
R/C car with steering
Common household tools
Dremel or drill (optional)
Garage sales are a great way to find a cheap R/C car. I searched for two weeks and didn't find one, so I bought one at Target that was on sale, and it came with a 10% discount for having absolutely useless drive wheels. I sometimes see cage traps at yard sales as well.
The first step is to carefully take apart the R/C car and extract the circuitry and the servo motor that controls the steering. My car was cheap and, after undoing a few screws, I was able to take everything apart by hand. A Dremel could be invaluable for this step. Be sure to maintain the integrity of the circuits and the steering mechanism. Save everything else for other awesome projects :)