When it comes to creating a positive learning environment in your classroom, it helps to focus on the Three R's. These are Rules, Routines, and Relationships. Creating clear expectations, consistency, and trust in your classroom benefits teachers and students alike.

Rules

Classroom rules help to establish expectations for your students. While they may seem simple, there are some important principles to stick by in order to ensure that they are utilized effectively.

Helpful Guidelines for Rules:

Provide 3 to 5 rules maximum and state them clearly.
Rules should be positively stated! (i.e. "Raise your hand to speak" instead of "No interrupting.")
Rules should be posted in an area visible to all (including the teacher).
There should be clear consequences that relate to specific behaviors. A child should know exactly what will happen if they follow or break a rule, rather than an assortment of consequences that you might pick from. You can use a "What if I do" chart to display both positive and negative consequences.
Rules should be taught at the beginning of the year and reviewed regularly. Therefore, all students will understand the pre-determined consequences for behavior. This helps avoid behavior issues resulting from a child feeling blind-sided by a consequence.

Here is an example of 5 classroom rules that are positively stated:

Routines

Expect the students don't know rather than assuming they do or should know!
Teach routines explicitly.
Model, practice, reinforce, and review often.
Make a list of your non-negotiables? E.g. no hall passes first 10 minutes of class, no pencil sharpening during silent reading, etc.
Consider various transitions within the classroom including arriving to and leaving from your class.
How do you want your students to access materials?
Are there any congested or excessively trafficked areas within the classroom?
Review your seating and desk set up after the first couple of days to a week of classes. Is it working?
Create a list of routines you expect to use the most and model them explicitly to your students

In this video, Anita Archer discusses the benefits of instructional routines in the classroom:

In Summary: using routines empowers both teachers and students:

Teachers are able to feel prepared and rehearsed and to engage in a sort of seamless "flow" while teaching.
Students become familiar with the steps of the procedure and are able to focus all of their attention onto the content rather than figuring out the task.

Relationships

Students come to school for 2 main reasons - Relationships and Success
Learn who your students are, what background are they coming from, what do they like and "geek out" about
Provide high rates of positive reinforcement to whole groups and individuals.
Beware they can tell a fake! Make your feedback positive, be specific, and real
Give yourself and your students time to get to know you and trust you.
Remember the differences between extraverted and introverted students.
Take care of yourself! Teaching is one of the hardest jobs. Eat well, exercise, get enough sleep!