When selecting candidates, check out their portfolios. The goal here is to see if their past experience matches with your project. Setting with a few contractors whose experience is most relevant is enough at this point, and the next step is to have an interview with them that will help you understand:
- what tasks they did in the past
- what the result was and how it helped their client
- if they had extraordinary, non-standard projects and how they approached them
You also want to find out if they had projects similar to yours. If yes, then it is a good sign. They are likely to have necessary solutions that will be implemented fast.