Seriously, your teaching sections will take up as much time as you allow them to.
Try limiting yourself to working 20 hours a week, or maybe start with 25. Do all of your school work first and put yourself ahead of your class. Here's why: You can still do a good job with a little less effort in your teaching because, you are not paid as much as a full-time professor. Your research into the _____ of 19th cent _____ is more important than whether or not every student in your class fully understands MLK's I have a Dream Speech, because ultimately, your work in your own studies will get you a job before whether or not one student will get the concept you are putting forth. This doesn't mean sacrificing your students for yourself, or maybe it does, but so what. Every experienced teacher, and I mean years and years on the job teachers...your 50 yo AP teacher from high school will tell you that you have to put yourself first or else your kids will never get your best. Because if you are so stressed that you couldn't finish your mid-term paper for ENG 565q because you were grading, you will not be an effective teacher. There are so many ways to evaluate students in the classroom that you need to carve out time over the course of two weeks or so to grade their papers, not because it takes for ever, but because you need to remain sane while doing it. However, you will kill yourself if you do not put yourself ahead of them and get done what you need to get done first. Then devote time to them. There is nothing so essential about a single day's lesson that it cannot be delayed if necessary. In fact your whole class objective for the semester should be less about covering material and more about hammering in a few, yes a few, extremely important skills. You can teach them millions of interesting facts and ways to analyze, but unless they have a foundation, they will get nowhere. And yes, keep the class simple and middle-grounded. The smart kids should have opted out of the class in the first place. And despite the notion of the wellfare state, not every kid is going to do well in college. Not every kid should be at Binghamton. This isn't social darwinism, but rather a recognition that there are different skill levels and different colleges to match those skill levels. There has to be a point at which your kids come toward what objectives you are getting at, not you always lagging for their sake. And I agree, office hours are a good place to deal with those issues. However, I imagine, given that you are graduate students, that you never had a professor coddle you. You probably had several who did the opposite, and it made you a better student and a better writer. Ask your kids to hone those basic skills and really challenge them to write well, but if they don't get it, they don't get it. Do not kill yourself. You are actually in charge of how much work you do.
That aside. We should get more money. That's a separate issue though. The general tone of the poster campaign has been: make us do less work. Not pay us more, which is both more productive and more likely to happen. It is so much cheaper for them to give us some more money than it would be for them to lessen our workload, so I say focus on the issue that helps you pay rent.
But seriously stick to a self-imposed 20-25 hour limit...keep in mind that the contract says an average of 20 hours a week, so on grading weeks, 20-25 is a stretch. See if you can't actually make it work for you, it's not entirely unreasonable. Also, make your office hours one hour more per week than is required, but then cut yourself off from doing any more than that. Do not answer student emails, because no email about how to cite a magazine is an emergency. Train the students to adhere to your policy. Here's another idea: create the 3 before me system, in that students must consult three sources and show that they have before they are allowed to ask you any question that crops up. It makes them do a little work, looking at dictionaries and talking to their friends in class. And it saves you lots of time.
Another thing experienced teachers will tell you: there is no single solution to making yourself more efficient or saving your time. However, if you do a lot of little things and have your students do a lot of little things, the time is there.
The last time someone posted a series of suggestions to save you time they got mocked, but what you don't realize is that they were speaking from a place of experience. Take some education courses or go work in a high school and soon enough you realize that a) you have it easy, and b) the stuff that works for high school teachers works because it works, not because those kids are 15.
I am rambling, but basically understand that education theory is well-researched and well-practiced and that the education kids in your classrooms who are finishing their MAT knows ridiculous amounts more about teaching than any of us do (unless you were one of those kids) and their theories and ideas would be really helpful.
Also, lastly, what is stopping anyone here from reading about professional development and working on it on their own a little but each week? Instead of just asking for the dept to do everything for you, which, yes it should be doing, why go do it for yourself. If you spent an hour a week reading about how to teach I bet you'd save twice as much time on the back end.