Biggest lesson of all was hire on one strict criteria - how long have you done sales just like this in the past for and what were the results? We made that mistake a lot too. Hiring great sales people that had never sold products like ours. It can work, but it's a risk you shouldn't take early on
Ask for screenshots of their performance
We've had multiple sales people who claimed to be #1 in their company and applied for a role. When I asked for screenshots of their CRM or to log in live and show me the leaderboard many went silent.
Sales people love to brag about performance so the real sales leaders will log in and want to show you. If they don't want to show you or dodge the topic it's a bad sign.