I should add some of the lessons I learned:
1) When you don't know how to do something you don't know how much you should pay.. and surprisingly it takes less time to learn than you would think. I wrote off learning Rails thinking it was harder then it was.. Sure it has its nuances, but in 45 days I've gained a really good perspective on building an app. But to learn, really commit! Build an app then when you are done, build another, and then another.
2) You have to launch and as soon as possible. Nothing else is as important. Motivation will die, money will be lost, and you'll have no idea what people will want unless you do. Period.
3) People telling you something is a good idea is not the same as people willing to use it. You can't base spending money and time off people, especially your friends, thinking something is a good idea. You have to test the waters (see point 2).
4) Join the community. If you are a reader of Hacker News, but don't code join the community of coders. I can't tell you how much more fulfilling it is to show up at local Ruby events as a coder, feeling welcome as "one of them" as opposed to as an entrepreneur seen as just 'hawking an idea'. Really, it's a great community of people once you are on the same side of the equation.
5) Distill your idea down to its simplest form possible. Convoluted ideas are difficult to pull off, difficult to convey to potential users, and difficult to convey to investors. Focus focus focus.
