In Xcode 5, you can make your comments appear in the Xcode opt-click pop-up help by using 3 slashes (///) instead of 2.
Example, you'd normally write:
//This comment has 2 slashes - (void)logout;
Instead, you write:
///This comment has 3 slashes - (void)logout;
This is especially helpful if you judiciously document your header files.