I have been working fulltime w/o pay developing my iPhone app, now it's closing to the release time and I think it's about the time start my own company. I wonder if anyone can provide some detailed guidelines as to the concrete steps of registering a software company, fundraising, equity issuing etc. I am located in Seattle
You do not need a company to sell iPhone apps. Apple allows individuals to sell apps in the app store. They send you a check, tell the IRS they sent you a check and you pay taxes on that revenue.
When I was in your situation few years back (selling Palm apps) I registered as DBA (Doing Business As i.e. Sole Proprietor) because all I wanted was to sell my apps under a company name. Registering DBA is the simplest and cheapest form. The details depend on the state but usually it involves finding a name that is not taken by some other business, filing simple paperwork with the city and paying a small fee. See this question for more details: How do I start a sole proprietorship and when does it start?
You can of course setup a more complicated structure like LLC or Corp S or Corp C, but the details for those are way out of scope for this forum and it's all really well explained in many places. I recommend NoLo (start with http://www.nolo.com/legal-encyclopedia/business-llcs-corporations) which has wonderful books on exactly those subjects (http://www.nolo.com/products/incorporate-your-business-NIBS.html, http://www.nolo.com/products/llc-or-corporation-CHENT.html).
As to fundraising, equity etc. - those are in themselves deep topics that would require an extensive treatise to cover generically and you haven't provided any information to reduce the scope of the answer to your particular scenario.
Knowing the little information you provided (i.e. you have iPhone app close to done), you don't need fundrising. Finish the app and start selling it.
Furthermore, it's incredibly hard (read: next to impossible) to get a funding for an iPhone app. A median revenue of an iPhone app is $600 a year - not an attractive opportunity for VC investing.
Investors have hundred millions of dollars to invest and limited amount of time to evaluate the deals. They are only interested in funding ideas that can become hundred million dollar businesses. Is your idea one of those? Can you convince an investor of that?
Don't invent yourself a lawyer, take a lawyer for this kind of stuff. Honestly, it's a bit of money (take a good one who has a lot of experience is startups and subsequent rounds), or you may pay the price later (big time).
That said, try to push your incorporation as far as you can (basically when you have to bring someone else in the team and pay them), so you don't rush into structure that don't fit your model.