As a personal rule, I speak to at least 2 current and 2 past employees after the first round of interviews. Saved me from way too many red flag teams.

This sounds like a good tip. I'll do that going forward

How do you get to know the past employees ?
I tried searching for past employees but I never get them. Any feature on LinkedIn?

How do you even know or get contacts of current and past employees of the team?