I am a former builder and contractor. Just because someone is liscensed does not make them skilled which means the most important item on your list of tips is to actually put 'eyes on 'former jobs' and you should understand that materials and labor usually run about 50/50 to be fair to the customer. Check it twice-cut it once.

Most importantly, look at the individual attempting to sell you his services...really look at him. instincts can tell you alot about a person.

Also. Watch a lot of "Holmes on Homes" or "Holmes Inspection". Every rerun if you have to. You'll learn a ton of information on "Doing it Right the First Time".