Setting Boundaries, Saying No

Lately I've run into many situations that require me to think about setting boundaries with students and what I am and am not willing to do. More specifically, I've had a number of students ask me for things that they see as their right and I see as me granting them a favor that will in no way affect my annual review or my tenure file. These include:

• A graduate student asking to meet with me to talk about a book project (that has nothing to do with her dissertation, and I am not on her committee, anyway). I happily agreed to the meeting, as it was during my office hours. I declined to read the entire book project.
• Multiple students asking for overrides into my courses, the caps for which are already set higher than they really should be. My usual policy is a flat out no, as students not being able to get into courses is really a problem to be dealt with by the administration, not me as an individual instructor (and if I let them in, and everyone else lets them in, then we're all doing extra work and the problem remains invisible). In the end, I let one into each of my courses, as I predicted/hoped that at least one person would drop. I was right about one class, at least.
• Multiple students asking me to do "honors options" with them. These I said yes to, as it ultimately amounts to me looking over an extra paper at the end of the semester, and offers the possibility of having them do presentations on their work (which might ultimately make class time easier for me).
• A student asking if she could "add" a credit to a 3-credit class because she is 1-credit short of graduating. I should have said no to that one but didn't, and now we're in negotiations of what kind of project she should do. I hope she realizes, as I keep adding extra requirements, that adding a credit hour means doing 1 hour of class time plus homework time each week. In short, reading one extra book and writing a short paper on it is not an adequate plan of study.
• Multiple international students asking to "sit in" on my courses. Said yes to one, no to the other, given the particular issues of the courses in question.
• A student I've never met asking me to conduct an independent study for him. That was an easy no freaking way.

There are others, but this list should provide a general sense of the things I am asked to do, above and beyond my actual job requirements. I'm feeling somewhat persnickety and protective of my time, what with coming up for tenure and trying to get pregnant and the dire budget situation that already means I will likely have to do more work for the same pay. I might like teaching, but I'm not going to be a martyr.