Ask HN: To employees of a startup that later got acquired/IPO'd

How do you figure out you picked a "winner" startup before joining?

Let me preface this with saying, I'll be so upset if the majority of answers boil down to having a lot of luck :D I've been burned out through a few early stage companies and it feels like it's all blind luck. Hopefully it's not all a guessing game and you can make predictions based on certain qualities and metrics of a startup at early stages.

As a bonus question: would you work for an early startup whose founder(s) have no previous business track record?