On a previous post, I gave the advice that when hiring a freelancer you will want to make a post on about 5 websites and select 1 person as a part-time hire from each site. That will be 5 workers. I would also like to add a little more advice to doing this effectively.
Even though you should hire your initial contractors part-time for a test run, it is probably not a good idea to let them know it's a test run though. If they know, they will be on their "best behavior." Just like with a photo, you want to catch them while they aren't looking. In your post, say you need a part-time worker for a short, important project. Also, mention that future work is possible.
After working with the contractors, you will know who is the best. That contractor will be your full-time hire . But don't burn your bridges with the other contractors. If you see a few good ones then tell them that you won't be needing them any further, but also let them know they will be on your list of contacts for future project.
After you are finished, you could even make another post. Find more good people. This is how you can build up a larger list of good contractors and even find a better contractor. If you run into someone who is better than you original selection, you can let your contractor go and hire the new one - if you think it is worth the risk. When letting them go, put them first on your list of go to guys and let them know that you will contact them again if necessary.
The above advice assumes you are doing a long-term job. This is a process that many people don't use. If they did, fewer people would complain about bad experiences.