A Warm Up.
All stand in a circle. One player holds a ball (something soft, safe, and easy to catch). The player says a word and throws the ball to someone else chosen at random--for example, "dot-matrix printer".
That person then says a category that includes the thing just said, and throws the ball to someone else. For example, "computer equipment". That person then says another instance within the category, and throws the ball. For example, "mouse pad". The next person says a new category--"vehicles for self-expression". And then back to an instance: "performance art". In other words, you alternate between categories and instances.
This warm up stretches your mind to be able to see many ways to relate to anything that you're given. It's a good preparation for Continuing the Game.
When you give an instance, be as concrete as possible. Instead of "book", try "War & Peace".
Make the category a plural (add -s): for example, "cars" or "books" instead of "car" or "book".
Try to see how far you can go in your category and still make sense.
Through experience, you get a feel for what is too narrow for your partners to use and what is too broad to suggest easy instances. Too narrow and there aren't any other instances. For example, if someone says, "War & Peace", then "books" is pretty broad, "Russian novels" is pretty cool, and "Tolstoy novels written in 1869" is too narrow.
example: Boston fern
category: houseplants
example: Venus flytrap
category: ways to show your friends that you have exotic tastes
example: playing the digeridoo
category: Australian skills
example: human sacrifice (note that your best guess is good enough; factual accuracy is not critical)
category: tests of courage
example: mumblety-peg
category: gambling games
example: craps
category: ways for Indian tribes to make money
example: prostitution
category: female-dominated fields
example: bank teller
category: people you've got to trust
example: your mother
category: people older than you
example: Mohandas K. Gandhi
category: peaceniks
example: George McGovern
category: losers
example: George Foreman
category: boxers
example: Rocky Balboa
category: great men