"Some problems with TF's only show up later, when they're grading," he says.
Even if those who spot a problem with the TF can have trouble switching sections.
Steele says she has sometimes faced obstacles in switching sections.
"Mostly I've had good TF's. A couple of times I haven't been able to invent a plausible scheduling conflict," Steele says.
Often large classes only permit section changes when students have serious scheduling conflicts.
John McHale, the Head TF of Social Analysis 10: "Principles of Economics," the largest class at Harvard, writes in an e-mail that changing sections for non-essential reasons is discouraged.
"Students are allowed to switch sections only if they have a time conflict," McHale writes. "We don't, however, look for proof of such conflicts, but take the student at their word."
Benjamin Berger, the Head TF of Moral Reasoning 22: "Justice," which filled Sanders Theatre in the fall semester, writes in an e-mail that it was difficult work out the logistics of sectioning changes.
"With around 800 students, sectioning as well as switching present huge challenges," Berger writes.
"In general, we try to limit section-switching to those students who have a legitimate conflict rather than those who simply would prefer a more convenient time slot," he writes.
Even with 800 students, the process eventually works out, according to Berger.
"Fortunately, with all of the switching activity, things tend to even out among sections, and someone who wants to get into one section usually can be matched with someone who wants to get out of the same section."
Many students, however, never attempt to make section changes in the first place, even when they are unhappy with their TF.
"By the time you get far enough into the course to figure out if the TF is any good, it's too late to switch," Gilman says.
Zack M. Gingo '98, says he can usually figure out quickly if he will like a TF.
"You can usually get an impression within one or two sections," Gingo says. "If a TF doesn't seem enthusiastic in the first section I think that's a pretty good tip off. I think that tells me either the TF doesn't want to be there or doesn't really care how he comes off."
Gingo, however, has never switched TF's. "Some classes the TF's were incredible and sometimes I guess I was just lazy," he says.