It's really simple. All you have to do is type up a clue. Then the next person who posts has to guess who the HP character is and then make a clue.

Example:
1st Poster:I'm a ghost of the Gyffindor house.
2nd poster:Nearly Headless Nick

I enjoy learning.
3rd Poster:Hermione

I published my own book
_____________________
Here is your first clue!

My nickname is Padfoot.