It's not always up to you whether people get kicked out, sorry to say; it's not a nightclub. Set up barriers, walls, razorwire etc. Don't leave spaces for people to sit drinks on your shit, put up signs etc If they don't fuck off do this: Instantly cut the music*, and tell them all to fuck off or you won't start it again * May not work out well if it's a bunch of rowdy drunk uncontrolled fucks and could make things worse