The first five minutes of a middle school math class are critical in setting the tone for the rest of the lesson. You may have learned how important it is to present the learning objective for the day, and also maybe a quick agenda of what to expect in class. I agree that you should do those things, but let's initiate the first five minutes of class getting the students to think. Once they have done some critical thinking, then you can continue with the learning objective and agenda.
Here are my three favorite ways to start a middle school math class.
1) Brain Teasers
My students loved when I gave them a brain teaser to start the class. They loved trying to solve it before their peers. The brain teasers were mostly math related, but not always, and that is ok. Like I mentioned earlier, anything that gets them thinking critically and using those problem-solving skills for five mintues is a great way to start your middle school math class. If you need some ideas of brain teasers to use, just look on the internet, there are many ideas.
2) Error Analysis
Collect some examples of your students' work with common mistakes that you see your students making. Cut off the name and also don't show the work if the student happens to be in the class, even with the name cut off.
Display the work at the beginning of class. You could use a doc cam, an ipad to an Apple TV or you could copy the student's work onto the board. Have the students find the errors, and explain the errors in their notebooks.
Another option is to save the work from year to year, and that way you are for sure not going to embarrass any student. Error analysis is a great activity for your middle school math students.
3) Math Prompts
Give your middle school math students quality math prompts, and let them write. All of my students had math journals to write in daily. When I gave math prompts, they were required to write at least three complete sentences in answer to the math writing prompt.