1. Avoid smiling and being friendly with your students.
While you should start each year with a tough stance and the idea that it is easier to let up than to get harder, this does not mean that you shouldn’t have students believe that you aren’t happy to be there.
2. Becoming friends with students while they are in class.
You should be friendly but not become friends. Friendship implies give and take. This can put you in a tough situation with all the students in the class. Teaching is not a popularity contest and you are not just one of the guys or girls. Always remember that.
3. Stop your lessons and confront students for minor infractions in class
When you confront students over minor infractions in class, there is no possible way to create a win-win situation. The offending student will have no way out and this can lead to even greater problems. It is much better to pull them aside and talk to them one-on-one.
4. Humiliate students to try and get them to behave.
Humiliation is a terrible technique to use as a teacher. Students will either be so cowed that they will never feel confident in your classroom, so hurt that they will not trust you ever again, or so upset that they can turn to disruptive methods of retaliation.
Once you've yelled you've lost the battle. This doesn't mean you won't have to raise your voice every once in awhile but teachers who yell all the time are often those with the worst classes.
6. Give your control over to the students.
Any decisions that are made in class should be made by you for good reasons. Just because students are trying to get out of a quiz or test does not mean that you should allow that to happen unless there is a good and viable reason. You can easily become a doormat if you give in to all demands.
7. Treat students differently based on personal likes and dislikes.
Face it. You are human and there will be kids you will like more than others. However, you must try your hardest never to let this show in class. Call on all students equally. Do not lessen punishments for students you really like.
8. Create rules that are essentially unfair.
Sometimes the rules themselves can put you in bad situations. For example, if a teacher has a rule that allows for no work to be turned in after the bell rings then this could set up a difficult situation. What if a student has a valid excuse? What makes a valid excuse? These are situations it would be best to just avoid.
9. Gossip and complain about other teachers.
There will be days when you hear things from students about other teachers that you just think are terrible. However, you should be noncommittal to the students and take your concerns to the teacher themselves or to administration. What you say to your students is not private and will be shared.
10. Be inconsistent with grading and/or accepting late work.
Make sure that you have consistent rules on this. Do not allow students to turn in late work for full points at any time because this takes away the incentive to turn in work on time. Further, use rubrics when you are grading assignments that require subjectivity. This helps protect you and explain the reason for the students' grades.