I think this is a bit better at explaining it than I might be. I wouldn't recommend following the directions to the letter, especially if you're not confident in your skills in dealing with electrical wire maintenance, but also because this is very general and you shouldn't go chopping up your car's wires. You can at least strat tracing before you drop the car off to a specialist, possibly isolate the general area of the short, and understand what you're actually looking for.
How to Find Electrical Shorts | eHow.com
EDIT: One thing I can definitely say that's mentioned in there is don't go hunting with the battery still connected. You'll fry your meter. And you don't need just an ohm-meter, just go get a multi-meter if you don't already have one, and ensure that it can read resistance in ohms, and you're good.