Keith Stuart wrote a fun piece for The Guardian called How to become an iPhone developer in eight easy steps. Which is based on the success of Ethan Nicholas (iShoot) and other iPhone developers. Nicholas left his job as a programmer at Sun Microsystems after iShoot rocketed to the top of the App Store charts and stayed there for weeks.
Anyway, here's the recipe:
He also concludes, as other have, that releasing a free/lite version is pretty much mandatory in light of Apple's resistance to creating an infrastructure for trial apps in the App Store.
iShoot was widely ignored for several weeks before Nicholas decided to produce a cut-down 'Lite' version which he made available for free. "it quickly became the #1 free application, and iShoot sales followed suit.
Tip: The Guardian