The "Literal" clue "Head of state?" or "Head of state, literally" is often used to clue the entry ESS in the grid, which is the spelled out version of the letter S. It can also be used to clue something that could be a prefix for STATE such as TRI or INTER. The clue "Couple of fellows?" could clue the word ELS. And so on.
Little tricks come to mind . . . "Gee follower" could clue AITCH or WHIZ.
Clues like this can add some entertainment value to your puzzle, and sometimes make it a bit more difficult that just using very straightforward clues.
Turning it around the other way, you can use a clue such as "V?" to clue an entry such as CIVIC CENTER. Occasionally you will see a theme that's made up entirely of these gimmicks.
This web site has a database of clues and answers that will help you see many such arrangements. If you don't have a "gold" membership, you can use the web site crosswordtracker.com or crosswordgiant.com for similar information. I hope this is helpful.