Some schools allow you to request a CT if you have one in mind. Remember that this is often a delicate, diplomatic undertaking which involves you, your University or College, a school principal, and a school teacher. Your CT will be opening his or her classroom to you under great trust and is going to contribute to a major portion of your teaching preparation. Some people believe this is THE most important component. The match between you and your CT can make or break your student teaching experience - if you let it.
Most folks agree that there is no such thing as a perfect match.
If you are wise, you will watch and learn. You may decide not to emulate your CT after your student teaching experience. Or, you may decide you want to be just like him or her. My point is that while you are a guest in that classroom, your job is to learn what there is to learn about teaching, classroom management, administrative functions, the roles of the teacher, etc. - not to dazzle the class and principal with your abilities. Sure you want to do a great job.