I realize that this is an old post, but I will be a TA in my school's physics department come next fall and have thought much about how to proceed with this role of responsibility.
From my experience during recitations, I saw that the common approach is that the students show up and ask questions about their homework (which is eventually turned in as a grade) and the TA offers hints or works through the problems. I am turned off by this approach because the students need not seriously think about their homework before coming to class.
I offer the following model and would appreciate any feedback. This model rests on the the premise that physics is not an easy subject and that the student must "practice" to become more efficient at solving problems. Practice encompasses the following: understanding the conceptual aspects of the subject, thinking about one's approach to solving problems, and studying a variety of interesting problems.
With that said, when students show up to my recitation I will not devote any time to the assigned homework. Instead, the students will be organized into groups and will receive a worksheet aligned with the content of their professor's lectures to complete. This worksheet will have simple conceptual questions and a few applicable problems that require more time. As the students work, I will proceed around the room to answer group questions. By doing this, I will see where the common problems in conceptual understanding are and can target these briefly by reviewing those answers. The same applies to the harder problems, but in this case I will review how to solve these by how to go about thinking about the problem, offering problem solving strategies (e.g. generalization, adding auxiliary elements, etc.), and requesting student feedback.
Questions regarding homework will be answered outside of class by email or during my office hours and only if the student has showed considerable thought about the problem. If these requirements are met, I will ask questions that help to guide their thinking process not solve the problem outright as I have seen some TAs do.