hmm, it depends not only on the profs, but also the course, at least in our school, we have like 4 physics I courses.
Yea, do the hws, do the labs carefully, and hopefully, whole-heartedly, although they might appear to be really boring (I think that there are talks about the differences between Intermediate/advance labs vs. intro labs).
About the hw, hmm, I guess it depends on the profs, but don't be scared if you couldn't solve for a problem for days. It is quite normal.
And the amount of time that should be put into hw. Well, I have heard that someone said that 2 hours per week, as far as I know, that is closer to the lower bound, although that might be for inttro courses. From my personal experience, it is normally twice of that amount, and up to 16 hours a week is not unheard of (although I really think that it is a bit exaggerated. And jee, when our prof heard it, he just simply nodded and thought that that is the RIGHT amount of hw...)
Do the homework solidly, because the same things would appear again and again. And if you didn't do well at first and ignore it, it would haunt you later on (from my personal experience again...)
And go to your profs' office hour (if there is one). Not just only for the sake of understanding the physics, which is nonetheless important, but also to search for potential advisor/research advisor. This is one of the advice that I have had before. Do well, really well in fact, in a particular course. Go to that prof's office hour regularly, and at the end of the semester, ask the prof if you can work for him. And boom, you are way ahead in the game!
Sidenote for research: During your early years of research, don't limit yourself to certain field that you want to study in the future. Some of them are in fact, just impossible to do for a freshmen, or sophmore, for that matter. So for example, I am going to do something with Particle Physics, analysis stuff. And I am pretty certain that I am not acedamically prepared until pretty recently! (and even now, I am not well rounded because I still need to start studying more on the subject). The same hold for theory research.
And about lab. Well, normally, intro lab is boring (and inaccurate, which could sometimes be discorouging). But still, try to work hard on it. Try to develop rigorous attitude because it would be useful later on. When you get like 40% error, try to analyze what was wrong (so a typical way of saying is, well, a few % from here, a few % from there. And at the end, it would accumilate to 40%).
I am not sure for other schools, but in my school, physics lab is the least time consuming one. I have heard of people from bio and chem labs saying that they need to spend 6,7 hours outside of regular lab hours in order to finish the write up (I guess those departments are more rigorous than us =P).
Ok, these are my 2 cents for right now.