Your main job is to do what you need to do to help the students in your lab understand and learn the material they are responsible for. Some professors will want you to actually do introductory lectures during the lab periods, while other professors will do all the lecturing and only require you to be available to work one-on-one with the students if they need help. You may be expected to make up lab quizzes, grade lab reports, set up lab practicals, hold lab help sessions for interested students, etc. Talk with your professor to find out exactly what is expected of you during the semester.
You are also responsible for keeping the lab clean and straight -- other labs will be meeting in that same room and will not appreciate walking into a mess. Even if your professor doesn't direct you to keep the lab straightened and cleaned, that IS your responsibility.
If your lab uses microscope slides during the semester, you will be expected to do a slide inventory at the end of the semester and do a thorough cleaning of the lab. Talk to your professor about this or talk with Dr. Wood.
And speaking of microscopes ... you must watch the students at all times to be sure that they are treating our microscopes properly. Do not hesitate to correct any student who is not carrying a scope correctly or who does not store the scope properly at the end of lab. We have a system in place to keep track of who is using a particular scope so you will be able to track down any offenders. Do not take this lightly.