Trial and error is probably a good tip. As for the go bad eventually comment, I'd suggest paying the good one a fair rate and they'll be far less likely to "go bad". No one like's to work for free, that goes for people who own trucks and tools as well as those who own BMW's and briefcases. Pay them poorly, not on time, argue about every bill and every cent and I'll argue who it is that went bad.
That said, I'd avoid Craigslist. The jobs a person gets from people searching craigslist are the best jobs to avoid so anyone looking for gigs there are also probably the best ones to avoid.
Hop in your car and drive around a nice, middle class neighborhood and look for people working on these houses. Avoid the ones driving $65,000 lifted trucks and the ones in rusted, 1991 minivans, no offense to either of these groups but the rest are probably what you're looking for.
