There are often mentoring programs, workshops, and other training for teachers when they are hired right out of college. They can get help with just about anything. There is often one exception, though--new teachers are usually already expected to be perfect with classroom management.
So, new teachers, realize that you probably won't have been trained well enough in classroom management in college. It may be up to you to catch up on your own. Trying to emulate your own teacher or following the advice to not "smile before Christmas" is not going to be enough.
Ask other teachers how they handle classroom management. Read as many books on the topic as you can. Read some blogs. Take it upon yourself to get ready.
Classroom management is one area that you will be expected to be great in before you even begin.