Establishing a few "small" level rules can make a big difference in the overall behavior of your class. Showing your students that there are boundaries from the beginning can send a message that they will be expected to behave in an orderly way.
The consequences you use may not even need to be anything more than calling the student out for the misbehavior. Do whatever works for you and fits your teaching style.
If the only misbehavior that you try to stop are the major issues, then you will likely have a tough time keeping things under control in the long run.
Start out by establishing some boundaries and you will have a much better chance of eliminating misbehavior in your classroom, both big and small.