That's an interesting question. I spoke at a lot of conferences, ran lots of stands for companies at trade shows, then made the leap.

If you're comfortable approaching and talking to strangers, and can talk with confidence about a technical product, that's pretty much all you need to get started.

Knowing a product inside out, being quite good with APIs in general, hacking prototypes efficiently together.. usually helps, along with having passion for tech and being a social person