There are some contractor review services such as homestars, angies list, service magic and others. They may be able to help you select a contractor.
If you are going high end, an architect can often manage this for you as well.
Bottom line is make sure you get apples to apples quotes. In other words, make sure they all are quoting on the exact same things.
We did a series of podcasts on basement finishing. Mostly oriented to DIY but you may find some information useful.
Basement Finishing Series