It's time for a new job

So here I am typing up my resume and wondering when I should tell my current boss (who doesn't handle employee turnover too well) that I want to quit.
It could be the hours. I've been working 4:00-12:30 4 or more days a week, which was fine when I was getting a good break here and there, but lately I'm lucky to get two days off in a row, and that is not cool with me. I have an assistant manager who constantly shows up 10-15 minutes late for every shift. He's stopped apologizing for this and I've stopped hoping this behavior would change if I brought it up to my manager. I learned very early on in my employ at this store that the manager and assistant manager have each others backs. I would find this admirable if not for the rumored reasoning behind it, which you can probably figure out for yourself.
One thing I have learned is that the best way to get along with people is to just accept criticism, and follow their correction. Even when I don't agree or am not responsible for something that has happened, I just take it. It's frustrating, because I sometimes get blamed for other peoples mistakes, but I find that trying to point that out never reflects back the way it should. So I am kind of stuck. Although I think the majority of the time I have earned the criticism that comes my way, so maybe that's not too important of an issue.
Anyway, the point of this post is: I am getting my stuff together and going to look for a new job. Not a retail job. One where I can sit at a desk and stare at a computer screen all day, and maybe have a boss like Michael Scott who I can make fun of on my luxurious weekend off.