The folks over at Packt publishing have published a nice succinct overview to get you started building your first iPhone app.  Of course it’s a Hello World! program, and, despite a few errors, it serves as a useful introduction, including a brief overview of the structure of the iPhone OS .

In order to make the example work

• ignore the references to FirstApp.m, the author is referring to FirstAppAppDelegate.m which was created for you
• you also need to remove [window addSubview:viewController.view]; from the applicationDidFinishLaunching method