stereotype noun a set of inaccurate, simplistic generalizations about a group that allows others to categorize them and treat them accordingly.
Here are some examples (in my mind anyway!):
A librarian is strict, uptight, wears boring clothes and possibly glasses.
A Harley-Davidson rider is a big, muscular, mean man who wears leather and boots and has tattoos.
We don't want cliched characters in our writing. It's boring! Let's show our readers how creative we can be by giving our characters a few UNEXPECTED traits/hobbies/interests.
Taking the above examples:
The librarian, who appears to be all of the above, actually takes pole dancing classes in the evenings.
The Harley-Davidson rider, who appears to be all of the above, is actually a gentle soul and enjoys tending his bonsai plants in his spare time.
I think my most cliched character is the wise mentor (you know, the character who has most of the answers and helps the hero along on his/her quest) and I'm having trouble figuring out how to make her unique and unexpected. Any ideas?