Word of mouth/referrals.
When you are searching for a company to work with one of the main factors you pay attention to is if you can trust the company. If you have a gut feeling that you cannot trust them, run. I don’t know the science behind it, but the gut is always right.
Who do you trust in your life?
Your friends, family, co-workers, right? If they told you a company to check out because they had a great experience with them, would you? The answer is yes, you would choose your friends recommendation over Google any day for the sole fact that you trust them. (if you find more trust in Google than your friends, find new friends)
Someone that has a great experience will tell all their close friends, family & co-workers which will domino effect into a flood of new customers. This also could help bring back a past client that came in, had a bad experience and never returned but they heard you may have changed for the better and will try again. All thanks to a friendship.
Same goes for when someone has a bad experience, they will go to hell & high water to make sure your company tanks.