Lifehacker links to this piece by Paul Graham, which I'd recommend to anyone contemplating or running a software startup - it's pure gold.
Here are my comments on his bullet points.
1. Release Early
That's because you don't really know what your future customers need until they've tried your product. Of course early release means a minimal feature subset, not a buggy Beta.
2. Keep Pumping Out Features
That keeps your users happy - you don't have to slavishly give them what they ask for, just keep them dazzled.
3. Make Users Happy
This attitude has to permeate the company - don't give the job to a walled off customer service team.
4. Fear the Right Things
Expect disaster, it's part of startup life, but don't worry about Microsoft or Google, it's the other startups that'll get you.
5. Commitment Is a Self-Fulfilling Prophecy
Some people may be committed by nature, but in my experience successful entrepreneurs are committed because they just had to be - they'd run out of cash, needed to fund a messy divorce etc. So make sure you burn your boats.
6. There Is Always Room
Markets are infinitely unbounded, you can always add value.
7. Don't Get Your Hopes Up
The natural state in a startup is failure - everything will go wrong. I once landed in Chicago to stage a crucial demonstration only to find that my both my demo server in California and its remote backup had gone down due to freak power outages caused by hot weather. This never happens when you're in a big company. So to stay sane, expect the worst.
8. Speed, not Money
Think of the startup as a way of accelerating the boring task of making money, so you can fit all the other things you want to do into your finite life.