How Should I Quit My Part-time Job?

I have a part time job, I've been there since the end of February and I get the worst hours and days, and not enough of them. The manager who is always on my shift is kind of a jerk and a girl who told me about the job goes to my school and tries to make my job terrible and boss me around even though she has no more authority than I do and she talks about me behind my back at school. I CAN'T ESCAPE! I'm going to give my two week notice like I should, but what should I say to the main manager (who I almost never see) and how should I do it, like in private? Any tips would be nice. Also I don't have another job yet, but I applied at another similar store and wrote down my current job as experience. I'm also applying everywhere else.

Suggestion:

Have you tried talking to the main manager about getting different shifts and days. I would do that first.

If that doesn't work for you, then set up a meeting with the main manager in private and tell him/her that you would like to put in your two weeks notice because the job is conflicting with your school (as it probably really is if you are getting the worst hours). You might also mention that you didn't feel like you could approach your shift manager about the situation.