If the exercise involves new equipment, get to know the piece of equipment and demonstrate how it works at the beginning of the lab session. Lab sessions offer the students hands-on experience. Your primary role as a TA , then, is that of a guide. It is a good practice to begin each lab session with a review of the purposes and procedures for conducting the experiment. Circulate among the students to make sure they are handling the equipment correctly.
Handouts can work as effective aids in lab classes.
If you are in charge of a computer lab, for example, you can prepare handouts that outline the logon procedures and steps for starting or shutting the computer. If you are a science lab TA, you can have handouts that explain certain standard procedures or complex equations and calculations. Evaluation of lab sessions is important. Check with your supervisor about grading lab reports. Explain the grading criteria to your students when discussing the assignment.