To put it simply, use the Elance Contractor Analysis and Selection (ECAS)!
This product was designed out of my own personal need to select the best candidates for my Elance projects.
That is why plenty of thought and effort has been put into the ECAS - because it is something that I myself use to make an accurate analysis of contractors. It is now in your hands as well.
In brief summary, what the ECAS analysis tool does for you is that it quickly and methodically compiles an analysis of the most important stats associated with a contractor.
The ECAS allows you to combine 3 main factors - Level, Rating, # of Jobs - into a single Score so that you don't have to rack your brain trying to decide who is really the best candidate. All important factors are laid out in front of your in clear detail.
Click on the link below for a closer look at the ECAS tool.