1. if (ethics != 100%) return(DontBother);
2. Regardless of paperwork, you're *married* to your co-founder.
3. if (CofounderMarriage == wrong) return(StopNow);
4. Customer first, technology second
5. Make your customers love you, everything else gets easier.
6. Evangelize, evangelize, evangelize. People love passion.
7. When in doubt, release. If you did #5, they'll understand.
8. Get constant feedback. You don't know your requirements.
9. Run out of cash and you're dead.
10. Have fun!
[EDIT 11. Accept feedback willingly and implement as appropriate. Thanks, idlewords.]