You know the saying, "You never get a second chance to make a first impression." This most definitely holds true for the classroom as well. You're about to make your first impression to your students and one thing I adhere to is "If you say it, mean it!" For instance, when it comes to discipline never use idle threats, for example: "If you don't stop talking you'll miss recess." Therefore, if the talking doesn't stop, recess must be missed. Always remember to mean what you say and say what you mean. Keep your expectations high, if not, how can you expect students to rise to meet them? And most of all, my favorite habit is to be fair but be firm.

For setting up classroom rules, determining consequences, handling all behavior types, dealing with parents, and using some great ice breaker worksheets, be sure to see 'Back to School Central'

Go slowly. With physicians prescribing drugs for drugs for ADD/ADHD, depression, bipolar disorder, panic disorder, vitamin D deficiency, iron deficiency, lack of fluoride, calcium deficiency, recurrent ear infections, obsessive compulsive disorder, autism, conduct disorder and anorexia, it is really important to do the research and be well informed about the choices of medications and their potential side effects. Just because adults are taking some of these drugs, doesn't necessarily mean children should be taking them.
See the Boston Globe's full article on Go Slow on Medicating Children.