The best is to use networks... your friends, your friends friends, your advisors friends etc. They'll be more willing to put up with a less than perfect product, and if you make them happy, they will be customers for life and tell their friends. We had luck with this early on at FeeFighters and it has served us well, as our customers almost always refer us to other customers. (B2B site lowering credit card processing fees via instant reverse auction)