I have used two very reliable websites: http://Guru.com and http://www.freelancer.com

You asked what to look for? Both websites offer reviews on all hired companies, so you can read the reviews and feedback.

Also, very important: Look for a company who actually answers your request and responds "personally" to your project. What I mean by that statement is that some people paste a canned response which they use for all responses. That does not tell me that they can do the job. Make people tell you how they will accomplish YOUR project and not just anyone's.

I also have used other sites, but these two were the best to me.

Bruce