Smart bidding, responsive ads, manual and original copywriting, good choice of keywords and campaing/ad group spread. What can be done automatic, do it automatically. But be sure you feed the machine with healthy food. You'll notice that a machine can do wonders in seconds what will you take hours to do. These days you can really rely on the machines algorithm. The ones that say you can't are those who'd prefer typewriters in the days wordprocessors on computers came to live.