I worked as a Physics Teaching Assistant (TA) while studying at UBC Okanagan. For 2 years, I taught between 1 and 2 lab sections per semester. I Helped students grasp concepts they may have had difficulty understanding in class. I then graded the worksheets they filled out.
My co-workers were other students, but we did not teach classes together. We met at weekly meetings to learn the experiments, where our lab manager helped us through any difficulties we had.
The hardest part was patience, however, the majority of my students were great to instruct and fun to be around, making the job great.
The biggest issue is that you must be a student to be a TA, and they restrict you to only 2 classes a semester, so that more students can get experience.