How did you find mentors?

I am hoping to startup soon, and I've come across a lot of advice to find mentors who have done this already, and can help guide.

My questions: 1. how did you meet your mentor and build a relationship with them 2. how has it helped you (or not helped you) 3. if you have not had a mentor, what is your view on this 4. any advice on how I could go about finding a mentor

for context: I'm ~8 years experienced, was heading engineering (~50 members) at a startup till recently. No real sales, marketing experience yet.