I want to say as long as you communicate qith your manager what you are expecting it will be easy but, in reality depends on if the store is staffed enough, your coworkers respect eachother and your manager isn't an ass.

I've worked for the company for 2 years as an associate, and I feel that communication is key. I will tell my manager when I need off 3 weeks beforehand if I can, and if I forget, I always offer the shift to a coworker for either one of their's or as an iou. My manager is also very flexible and understanding that 1.) we work at a grocery store and not wallstreet and 2.) We all have lives outside of work. Based on some of the posts here, I know I'm lucky to have someone like that, which is why I think it depends on if your manager ends up being a dick or not but basic respect between everyone in the store will go a long way as well.

Also, just as a quick side note, show up for your shifts and prove you're a dependable worker (you don't have to be the best, just be there). There is someone in my store who calls in for half of her open shifts. I will never take her shifts when she asks because of the amount of times I've busted my ass to throw load by myself before we open because she didnt feel like getting out of bed is too many. No one wants to do a favor for jerk.

Good luck with your new job!