Unfortunately not all contractors are tech savvy and some contractors don't want a website or pay a fee to be on Angie's List, Home Advisor, etc. Contractors need to pay an advertising fee to appear on these websites.
Some home owners will use word of mouth thru friends, colleagues, etc. who have seen renovations in their friends homes and liked the work done. Others will use online reviews before hiring somebody.
Best advice - ask family members, friends, co workers, etc. who they used and make a personal visit to their home to check out the work yourself. Then if you like the work done, hire that contractor. Online reviews can be good but I've heard some negative reviews don't get published which means the good reviews are lopsided.