For an absolute beginner a good way to start is by following an online course in iOS development:
http://www.hackrocket.com Will soon launch an immersive three-month program to teach absolute beginners how to build iPhone and iPad apps
http://teamtreehouse.com/
http://www.lynda.com/iOS-tutorials/iOS-SDK-Essential-Trainin...
http://itunes.apple.com/itunes-u/ipad-iphone-application-dev...
http://codelesson.com/courses/tag/Mobile
You can also try to learn on your own. Here are some of the best books:
- iPhone Programming : The Big Nerd Ranch Guide
- Cocoa Design Patterns
- iPhone App Development : The Missing Manual
- The iOS Developer's Cookbook
- Cocoa Design Patterns
- Head First: iPhone Development
Once you start developing http://www.stackoverflow.com is an invaluable resource