Excellent article on starting your own software company
Eric Sink has a great article in the MSDN about starting your own software company.
They key points that I strongly agree with here are, "Ideas are worthless" and "Choose your Competition". These are two of the most important concepts I've always kept in mind while working on NormSoft.
I'm also happy to say that NormSoft is the exception to the rule with regards to seed capital. We started with $0. My initial legal expenses of $500 were paid for within a month or two. NormSoft has paid for everything since then and has always been profitable (albeit not very profitable for the first 3-4 years!).