Hi Matt,
Picking a good contractor is one of the most important parts to the success of a project.
Once you have the scope laid out, ( written down ) and plans drawn you can put it out to bid.
Having a job walk at the beginning will save you a lot of time in the interview process.
I invite three contractors to look at the job at a set time.
I walk them through the project, give them the schedule we will adhere to and during this process I give them a list of the items I will be supplying, toilets, lights ext. There is no reason to pay markup on items you can buy.
At this time I also get their references and I call them. Ask the references if they stayed on budget and schedule and how was their communication.
You will also want to get their license information, in my state in order to get a license they will have to have all the necessary insurances and bonds and keep them current.
You can also call the state contractors board and look up all their information. The board will let you know if they have any leans, any complaints or issues.
When you sign a contract with them make sure it includes the schedule. This will give you leverage if they start to fall behind.