Be yourself, not someone else. Be happy as who you are.
Massie does have some good qualities.
Try to have some slightly-less-popular friends, as well as some popular ones. This doesn't mean that you should try to befriend the geekiest girl in your school, but some of the girls who are nice and smart, though not quite "popular material" can make great friends. And who knows... maybe you can help them become more popular.
While you don't have to go around telling the whole world that you are not perfect, confide in a few of your good friends. Have a good friendship with them, instead of acting like you are better than they are, like Massie does.
It is possible to Be Popular but Not Mean.
Use common sense. Again, the Clique books are fiction. In the real world, someone who is that mean to everyone gets hated on and ditched by his/her friends, no matter how popular or feared he/she might be. People don't like being walked over.