This will go over a quick run through of using NSUserDefaults. This is the class to use to save user preferences for example. It is pretty straight forward.
This is how you save data.
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
// saving a string
[prefs setObject:@"test" forKey:@"stringVal"];
// saving a int
[prefs setObject::23 forKey:@"intVal"];
// saving it all
[prefs synchronize];
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
// getting the string
stringVal = [prefs stringForKey:@"stringVal"];
// getting the int
intVal = [prefs integerForKey:@"intVal"];
That is it.. pretty simple.