1. They have to be something generic, not too specific, like "a table" instead of "a chestnut-brown coffee table"
2.No changing your mind along the way. That's just plain annoying.
3. It'd be real helpful if you post the answers to the questions asked so far so that it's easier to read. e.g.
1) it's not alive
2) it is made of wood
etc.
Note: This rule is just meant for the person who's the question answerer (or whatever you call it), but if you want you can do it too

4. No objects that are inappropriate or disgusting.