A good startup is one which...
Changes something. A good startup is one which doesn’t have to spend loads of money on marketing, because you can’t fail to notice it. Spotify is a good example - people queued up to use it!

The most important characteristic of a startup founder is...
Stubbornness, stubbornness and stubbornness. Apart from that, strategic thinking, focus on your vision, and belief that you’ll succeed. It’s also important to be able to communicate your idea and your vision to the rest of the world. It helps if you can work well without sleep too ;-)