Think of a five-letter word. Your opponent tries to deduce it by guessing five-letter words. You state how many letters each guess shares with your word. It generally takes five to ten guesses to solve. The winner of a round is the one who needed the fewest guesses.
Avoid words like "spare" that have lots of anagrams, since no positional information can be given. Words with odd letter orders ("vodka") and repeated letters ("eerie") are hardest (unless your opponent hits you with obscurities such as zloty).