Discuss with your instructor and/or lead TAs if there is a preferred format for discussion
Look up where your classroom is—it may be a good idea to actually visit the classroom in order to determine how long it takes to get there, what technology/supplies you may need, etc.
Here are recommendations for facilitating the first discussion of the quarter:
The first discussion section sets the tone for the rest of the quarter. It is strongly encouraged that you set a precedent for the rest of the quarter with the way that discussion is run and the announcements you make.
Arrive at the classroom a few minutes early, equipped with any notes, writing materials, or technology you will be using.
Start promptly on time.
Introduce yourself.
Set expectations: some matters that one can set expectations for may include:
When students can expect replies to emails
A description of the format of discussion sections
A brief personal background on yourself, such as hobbies or hometown
Plan on using the entire 50 minute time period; make sure to bring extra material if you run short.
For the first week, if there is not much material to use, it's acceptable to go over review material from prerequisite courses.