As Head Teaching Fellow, you are responsible for the organization and efficient operation of both the course and its TF meetings. The tips below are designed to help you in those efforts. [Note: Some professors take a more hands-on approach to TF meetings than what is assumed here; adjust accordingly!]
1) You can never be too organized. Before the semester starts, sit down and figure out the frequency, time, and duration of your regular meetings, and what you hope to accomplish during each one. Goals can be as simple as making sure all TFs are prepared for the upcoming week, or as ambitious as preparing a midterm or final. Set these down in stone so that both you and the TFs know the general timetable for the semester.
2) Pick a good time to have a meeting. Don't schedule meetings too near to the time for the section meetings of a course. (Meetings on a Monday tend to do this, unless they plan for the week after.) Allow a lot of time for meetings: they go faster than you think. One hour is the bare minimum for a large course; 1.5 or 2 hour meetings are much more productive, and allow all TFs to voice their opinions during a meeting.
3) Have TFs run a practice section. Divide the TFs into groups of 2 or 3, who are responsible for a specific week or a segment of the course. This includes handouts, preparation of slides, etc. Have the group lead the other TFs (particularly new TFs) through a sample section for that week. This means a) TFs will be prepared to teach section that week b) all TFs will be teaching approximately the same material (a great worry in a large course!) and c) TFs do not duplicate handouts and work unnecessarily, saving labor for everybody.
4) Set up a time-table for TFs to return work to the students, and check on them during the meeting. Tardy TFs will be a major and justifiable complaint from the students to you, and it is not fair to have some TFs return work up to 6 weeks later than others. Remind TFs that undergraduates have strict add/drop dates, and that students need to have some idea of their grade at all points in the course.
5) Grade sample papers as a team. Before a heavily-weighed written assignment, xerox an average paper (something you would give a B) and hand it out to all the TFs. Have them read it and then mark it with a grade. Discuss what grades were given and why (I've seen the same paper get everything from a C to an A-.) From that discussion, come up with guidelines for an A paper, B paper, a failing paper, etc.
6) At the beginning of the meeting, go through a list of what you hope to accomplish. (I usually put a list on the chalkboard.) This keeps the more combative TFs from gabbing forever about topic X-- if they see that topics Y and Z still need to be covered, their instincts to end the meeting usually overpower their instincts to argue. E-mailing TFs in advance about the agenda of the meeting also expedites speedy sessions.
7) You get $75 per TF (subject to change in later years) for vittles for courses that meet ten or more times per term. I served lunch (sandwiches and drinks), which provided a convivial atmosphere (perhaps too convivial!) Afternoon TFs meeting can feature the occasional treat.
8) Don't be afraid to be assertive. As Head TF, you have a firmer grasp of organizational matters than the other TFs, and know best how to run things efficiently. Ask for advice when you need counsel, but don't let a recalcitrant TF second-guess or harass you, either during or outside a TF meeting. It may be awkward dealing firmly with a colleague, but it might be more disastrous to allow a particularly vocal TF to take over the meeting. Offer to discuss the matter after the meeting, or with the professor; don't allow time to be wasted on petty matters. If necessary, lay down the law.
9) Be wary of e-mail as a tool for communication. Most TFs read their e-mail very cursorily, and are not sufficiently inspired to respond. If you place the same e-mail in front of the same TFs during a staff meeting, you will find that not only do these TFs have strong opinions, but that they will voice them vociferously. Some ask why you didn't query them for their thoughts before-- even when you have!
10) The structure and timing of staff meetings changes toward the end of the semester. You will not need as many business meetings; you might even skip a week or two. But you will need to have a final grading meeting-- set up this time well in advance (at the beginning of the semester.) Otherwise, you will find TFs taking off for vacation, etc, before all TFs can meet to decide final grades.
11) Bring a laptop computer to the meeting. Any changes to the wording of a syllabus or an assignment can be made on the spot, and printed out directly after the meeting. This will save you lots of time in the long run.
12) Have TFs help you clean up after a meeting, particularly one involving food! Little things like that make your life so much more pleasant.