How do I give an "identifier" to a view controller within my storyboard?
As the Image suggests! Hope it helps!
Then to use it you call:
[self.storyboard instantiateViewControllerWithIdentifier:@"YourViewControllerID"];
Updated for XCode 8 and Swift 3.
instantiateViewControllerWithIdentifier is now instantiateViewController(withIdentifier:).
Setting the storyboard ID:
In the identity inspector there is a field Storyboard ID. You could enter the class name here and then use this identifier in instantiateViewControllerWithIdentifier:.