The very first step to creating your very own iPhone app or game is to apply to Apple's iPhone application area. This process will take several days. Plan ahead!
I chose to apply before I bought my actual Macintosh computer (as I did not have one already). This way if they rejected me for some reason I was not "stuck" with a computer I did not need.
To begin you go to the Apple iPhone developer area. That can be found here:
Apple iPhone developer area
Fill out the forms that are online there. You really want to apply as a business so that your apps show up with your "business name" rather than your personal (actual) name and information. It makes sense for privacy reasons.
If you are not yet a LLC or DBA, why aren't you? These are critical for legal protection and are very easy to do. Take that step first. Creating a DBA for yourself should be free, and you can do that at your local town or city hall. If you want to create a LLC, there are many books which can help you through the process step by step. It's well worth doing, but it will take you a little time to set it up properly. Make sure you take the time to read through the books, figure out your plan, and then write up your legal application with the description that suits your needs. This is, after all, for your legal protection. You want it done properly.
So, when you're ready with your DBA or LLC, fill in the Apple forms. Once you fill those forms out, you'll need to wait for them to verify you. Part of that will be them asking you to FAX them your proof of being a LLC or DBA or whatever you are. When I applied in February 2010 I got the request about 12 hours after I submitted my forms.
I FAXed in my LLC documentation. Four days later they called up on the phone to say they were all set. It was at this point that was able to go online and I paid them the $99 (or $105.19 including tax) for the year access. About an hour later I had the activation code and was all set!