Former Mizzou RA. (Well, Mizzou calls them CAs or PAs.)
Do not get busted for drinking or toking up in the dorms.
Do I know that's a spliff in your hand? Yes. Am I aware that there's more than just Dr. Pepper in that bottle? Also yes. Do I have any clue what twenty people in a tiny room drinking Natty sounds like? Affirmative. (Hint: it sounds like a quick door slam as I walk by followed by sudden silence.) I just had better things to do.
So how do you avoid getting busted? Don't be too loud too late too often. Seriously. That's it. You could avoid drinking in the dorm altogether, but come January, I don't think that's realistic.
Why should you care? Technically, you can get booted from the dorms for seemingly minor stuff that the insurance company takes very, very seriously. It happened to one of my residents. He was an idiot and got wasted and disassembled his smoke detector so he could smoke in his room. So he got kicked out with one week's notice. It sucked. Further, a write-up counts as something that you have to report on grad school applications, and if the police also respond... well, the hits keep coming.
Honestly, most RAs don't like writing people up. I preferred talking to people, recommending fun things in town, and chilling with people on my floor. And you get free room and board, which was the dopest thing imaginable as a broke college student. So most of us tried not to hassle people unless they got obvious: too loud, too late, too often.
You'll find an RA or two who really like hassling people. Keep an eye out for them. But most of them have normal lives and will look the other way as long as you don't give them a reason to do otherwise.