I had to learn Xcode, the Apple program for developing apps. Some books and the internet provided good sources of information. I did basic reading about Objective C (the programming language), then moved on to more practical stuff.
iPad Application Development for Dummies was good. That was a 2011 edition, and Xcode evolves quickly, so this type of book get out of date very fast. I notice the same author has a new edition for 2013: iOS 6 Application Development For Dummies, which I would recommend.
Even better was Sams Teach Yourself iOS 5 Application Development in 24 Hours by John Ray. The 2013 edition from the same author is Sams Teach Yourself iOS 6 Application Development in 24 Hours. This book is extremely well organized and well written. Maybe you could read the book in 24 hours, but it probably took me about a month to work through it, since each chapter is a project. You can only learn by doing. The explanations were excellent…I finally could really see how to implement what I wanted in my app.
The next level up would be Ray Wenderlich’s tutorials on the internet. These are deeper, a little more difficult, but excellent. I downloaded the pdf’s for iOS 5 and iOS 6…well worth the money.
There are many other tutorials and discussions on the internet, including YouTube videos. These were useful when I came upon some issue in implementing what I wanted. Searching about the problem would usually provide an answer.
My favorite things in Xcode to do what I wanted: Storyboards, Auto Layout, Tab Bar, Collection Views, and Animating Images.