Using SQLite 3 on the iPhone is really not that different from using it on any other platform. You should read the general SQLite documentation.
In your iPhone app, you usually open your SQLite database in the applicationDidFinishLaunching:
method of your application delegate. After that, you can just use your database.
I've used Gus Mueller's FMDatabase classes on the iPhone. They provide a thin wrapper around SQLite.
A final note: It seems CoreData will become available on the iPhone with OS version 3. You can use SQLite through the CoreData framework.