Make sure communication between yourself general contractor and subs is abundantly clear on every single detail. Walk through together to make sure.
Always get backup contractors because they get sick, die, leave you etc.
Make sure contractor has his name or company on the permit
Check real estate commission for licenses of realtors
Check secretary of state to make sure contractor is licensed
If you have mold, asbestos, radon make sure the contractor is certified to remove it.
General contractors do not like to work with subs that they do not choose
Project manager can not have too much going on or else they will neglect you
Make sure you get the general contractor sign over a document regarding he will be responsible for paying subs because you do not want his subs to turn around and sue you because they say he did not pay them
Get the names and phone numbers of all subs
Record all phone calls. (This is legal in most states only a few are against)
As soon as final inspection is passed contact the city inspector for the certificate of completion or occupancy (depends on state). You may have to call or visit the office more than once to get it.
Speak with your bank to find out the best ways to make payment.
Don't dismiss any deception and question all body language no matter what their title or position is.
Don't trust all recommendations that you see on the internet. People go on fiverr and pay people to give them glowing reviews