Hire people who are going to do their best work ever, for you, after having partially but not fully mastered everything you want, via their previous jobs. It's easy to evaluate a resume. It's harder -- but not impossible -- to assess potential. Working inside a big tech company for six years, I saw that PM hires were done almost entirely on pedigree: find me another Stanford grad. These tended to produce a lot of fast exits as well as some comically bad and totally predictable fails.
Engineering hires were done on hunger, drive, scrappiness (and networks). They fared better.