Search Engine Marketing
The first thing we usually find in a new account is money going to broad terms that look relevant and are not. An emergency plumber bidding on "plumbing" pays for students doing homework. A clinic bidding on a treatment name pays for people researching it for a school project.
Tightening that is where the fastest gains are, and it costs nothing extra. Then we make sure the page people land on matches what they searched, and that you can actually see which clicks became customers.