I have been in the construction industry working with contractors and sub-contractors directly for over 9 years now. (My dad was a GC). The Home Depot suggestion is good. Asking at your local supply houses is a great way to get referrals. They will know who is staying on schedule (because they order up-front, instead of constantly calling in emergencies), and they will know who pays their bills.
In addition, I like to ask the contractors they have to work with. For instance, if you are looking for a good GC, ask your favorite Electrician, Plumber or HVAC contractor. If you are looking for good subs, ask the sub contractor that has to follow them. Like, ask a painter who is their go-to drywall contractor, or Vice versa. Ask your HVAC contractor what Electrician and/or Plumber they like to work with. Its the people that have to work with the contractors to stay on schedule and budget that will give you great referrals for other dependable contractors.
Just my two cents.
Laureen