How do I tell which sales hires will ramp and which will flame out?

You can hire now, but predicting who will ramp and who will flame out still eludes you, and honestly it eludes almost everyone. People are not resumes, and an interview is a short window into a person's best behavior. Missing on a hire now and then is not proof you are bad at this. It is proof you are doing something genuinely hard. Still, the ones who get better at it are not reading minds. They are looking at the right signals: not polish in the room, but evidence of how the person actually works. Have they succeeded at something hard through their own effort? How do they respond to a setback? Can they learn fast in the interview itself? Charm predicts a good interview. Grit and coachability predict a good ramp. So build your questions around what people have actually done, not how they present. Ask for specific stories of struggle and recovery, and watch whether they take feedback in real time. You will still miss sometimes; everyone does. But hire for evidence over charisma and your average will climb, one better read at a time.