Craigslist is a great way to find vehicles, but you have to be super patient. That goes without saying when looking for a used vehicle in general though, never be in a hurry and never feel pressured. If someone else gets it bought before you then so be it, there are lots more out there probably at a cheaper price.
I keep lists of possible trucks I find and check on them every few days. Sometimes they go quick and I get the "post has been deleted by author" but a lot of times I'll track the same post for weeks if not months. This gives you bargaining power galore but then again some people just like sitting on overpriced autos. Heck I've had my eye on a mid 80's beat to hell short bed that is local. Other than needing a battery, driveshaft, wheels and tires, steering column and all the sheet metal replaced, it's an easy builder. Oh yeah it does not start but "is probably an easy fix".
Has been on CL for almost 2 years now for $800.
*edit*
It also helps to let your fellow truck brothers know what you're looking for in a round about way. Just imagine another 50 eyes looking for you between KS, OK and TX and sending you links when they find something that you might have missed otherwise.