-I would anyday recommend Raywenderwich tutorial. They are just awesome and so easy to follow.

-http://www.amazon.com/Programming-Objective-C-Edition-Develo...

-Just a problem which I tried to solve. Was searcing for one but didnt found any good solution.

- Lack of research, just creating app is not enough, you have to market your app. Also, Lack of time was my another problem