I think the best place to start learning is going through the Stanford lectures notes at http://www.stanford.edu/class/cs193p/cgi-bin/drupal/download... and watching the videos at http://itunes.apple.com/itunes-u/ipad-iphone-application-dev.... The strategy should be to finish one lecture in a day or two without rushing to the next lecture. Finish up the assignments and if you get stuck somewhere, search, learn, repeat. This way you would have learned quite a bit on specific topic and would be comfortable on the next topic. By lecture 10 you would be itching to write your own app, but don't succumb to the temptation and keep on finishing up the lectures. May be after lecture 18 you can explore things on your own. HTH