How does one run tryouts for junior high track and field?

I am a junior high (grades 6-8) track coach. Our track team has always been a no-cut sport, but this upcoming season we are being forced to cut. I can't even fathom how to do this since there will be kids trying out who have never competed in track, much less even know what all the events are. In addition, many kids are in multiple events (open running event, relay team and a field event). Is there anyone out there who has been involved with JH track who can share with me ideas on how to run try-outs? We can only do try-outs for 3 days, so there isn't really time to give instruction, and some events absolutely need it. I don't want kids who've never thrown a shot put before trying it without proper instruction first.