The single most important thing that you can do to increase your chances of getting into Y-Combinator is to do what you should be doing anyway: going full-speed ahead on your startup
Exactly. We're impressed by teams that get things done, and unimpressed by teams haven't even started to build something. I've often found myself thinking, "If you think this is so great an idea, why haven't you spent some weekends building a version 0 prototype?"
