I keep a notebook in my pocket, and I write down all the stuff we could ever do with Foursquare.

If there's something you want to build, but the tech isn't there yet, just find the closest possible way to make it happen.

Don't let people tell you your ideas won't work. If you're passionate about an idea that's stuck in your head, find a way to build it so you can prove to yourself that it doesn't work.

Don't let other people distract what you're doing. There's always haters.

Forget about where you want to be and go out and build stuff. Dodgeball came from being bored at work... things happen because you make them happen. Stop sketching, and start building.

Hire the best people you can find. This was kind of easy in the early days of foursquare - we hired our friends who were really passionate about the stuff they were building. We have a superstar team not just because their resumes are so strong, but because they've been passionate, thinking about and tinkering in this space forever. Those are the people you want to surround yourself with.

I'm still a really shitty programmer, but I know enough to hack a prototype together.