The instructor usually handles introductions in this case. It is important that you maintain an air of professionalism in the class. One should be dressed in business-casual attire and be attentive during the class. If you are expected to keep office hours outside of class, be punctual and approachable during them. If the instructor asks you to introduce yourself, give your name and how far you are into your program. You can also mention your hometown.

The most important thing about being a teaching assistant is to be approachable and helpful but to establish boundaries between yourself and the students you help. In most circumstances, the instructor will have duties for you to fulfill, such as grading or tutoring. The instructor will probably explain all of this to the class on the first day, so the need for introductions should be minimal. Assisting an instructor is a good way to gain real-life experience in the world of academia and teaching. If one takes one's duties seriously, one should receive very beneficial experience.

It can be a tricky tight-rope to walk as you are both a peer of your students and, to a certain extent, an authority figure in the classroom. Always present yourself with a certain degree of professionalism. Business-casual attire should do. I imagine that the professor will introduce you, but you will want to have a few words of your own to add.

Keep it simple and short. Introduce yourself with a bit of background and why you are particularly interested in the topic of this course. Try to sound knowledgeable without coming off as a know-it-all. Make it clear to the students that you are there to help them and that want them all to have a great experience in the classroom. You are a resource to help them succeed. Provide them with your contact information and be clear about what type of situation they should reach out to you. Most important is that you sound genuine and eager to be there.

The most important thing in this situation is to remain professional and establish a level of respect and distance from the students. That’s not to say you can’t be friends with them, but you must be able to separate the coursework from anything personal and make it clear that you will do so.

Typically, the professor will take care of the introductions, but you may want to elaborate on your background and experience and how you can be of service to the other students. In the end, the best thing to do is establish a level of professional separation so that the other students do see you as a resource and superior in terms of the class, because that will be most helpful to them and allows you to work most effectively.

Usually, the professor of a course will introduce teaching assistants to students on the first day of class. If you are asked to say a few words to introduce yourself, you want to convey professionalism, with a sense of helpfulness but with clear boundaries.

As first impressions count, remember to dress in a "business casual" style -- khakis or nice jeans and a collared shirt rather than a t-shirt and shorts. Give your name, and a bit of your background (your major, where you are in your program) and then describe briefly what you will be doing in the class and how you can help students. You should also describe how students can reach you if they have questions outside class hours.

Set up a teaching e-mail account (you can make a free one on gmail or hotmail if your school won't give you an extra) completely separate from your regular email, but linked to its own GoogleTalk or Skype address. That way you can respond to email queries from students and even hold virtual office hours but in a manner that makes clear boundaries between your role as a teaching assistant and your life as a student.

The main issue you will need to negotiate is how to present yourself as a helpful peer while at the same time remaining separate from the other students in your identity as a teacher.