How to not be a doormat?

Hi everyone! I (23F) just secured my first apartment. I’m still in college. All my friends (19-23F/nb) are also in college, but they all live with family still. I haven’t even moved in yet (move in 8/8) and they’re already planning hangouts and whatnot.

How do I establish firm boundaries in the kindest way? I want to tell them that although my apartment is a safe place and welcomes all, it must be on my terms and that cannot be disrespected. I like my space and that’s why I’m living alone. I don’t want them to feel like I don’t want all of them there, but I want to ensure they don’t feel they have a right to my place just because I’m in total control of who goes there. This means that no, we cannot use my house as a hangout every time. No, you cannot stay till 3am when I have a 8:30 class. No, you cannot drink in my dry house.

How can I be firm without being mean, and how do I know when to say something? Now? When I move in? If it becomes an issue? TIA.