Hey OP! Awesome that you're doing this and trying to get things rolling at your home hill.
As mentioned above, keep things simple.
Pick a date in advance. It's nice if that date doesn't coincide with other events in the area, but for a smaller event like this, you'll probably be getting mostly your local riders anyway. So pick a date that you think you'll have the snow by for whatever comp and go with it. Obviously if it's raining sideways or the park is buried under 12 feet of snow you might have to postpone, but having a date in advance let's you get the word out, and people can make a plan.
Make a flyer for the event. You can just whip something up in photoshop. Find a good shot of somebody on one of your rails at your mountain and throw the contest name/ info on that.
When is it?
How much is it?
What time will it run? What time does registration end, what time is the riders meeting on course, when does the event actually start.
Any rules like helmets required etc.
Once you set a date talk to some local shops. If this is a small even don't worry too hard about getting a ton of stuff. If the contest is cheap like $10 it's not a big deal if the prizes aren't epic. Obviously take the best prizes for 1st place ski and board and then go from there. Do this in advance if you can so you can see what you're missing. Maybe you still need 3rd place prizes? Maybe you need to spice up first place a bit? Talk to the mountain and see if you can throw in a lift ticket for first, or maybe a free meal in the cafe for 3rd. Stuff like that that you can do in house.
As far as the setup. CLEAN IS EVERYTHING. EVERYTHING. A down bar and a flat rail set up clean, with nice smooth takeoffs that are built well is better than the most elaborate but shitty built setup imo.
Remember that people have to ride the stuff you build. What is your target demographic? You're probably going with mostly locals. How good are the locals at your mountain? Give them something that they can hit, but maybe has some challenge to it. If this is all ages, it's good to throw a box or smaller rail in there because you will likely have some lesser abled shredders trying to get down. That's fun though. Maybe somebody's best trick is getting sideways on a box, but if they're coming out to support your event, fuck it, embrace it.
I personally like to plan my setups out in advance and build them in sketchup or draw them out in advance. It let's me visualize the space and what will work best for a certain event outside of my head. I also use the sketchup models to promote the event in advance, especially for rail jams. If you're going to build something sick, it's nice to let people know in advance, as you might get some people coming in from nearby areas that don't normally shred your mountain. The downside is that if you put the setup out in advance, you have to deliver that setup, or people will be pretty butthurt. So if you aren't sure what you're doing, it might not be a great idea, but you can still draw your plan out, and just not share it.
Make sure the different departments of the mountain are aware of the rail jam. If there are marketing people they can help boost it on social media. You want your grooming staff to know they're going to have something going on, that might require some additional work even if it's just pushing out a small pad. You want patrol to be aware for obvious reasons.
If you make flyers you can hang them up around the mountain, ask some of the local shops if you can hang flyers there as well. If you have a park page on anything through it up there, if not you can just mention it to peoples on facebook. Tell your friends spread the word. The more people the better for the beginning. If you don't get people out, it's tough to get traction for other events
Stay local imo, for small events for prizes at first. If you haven't done any events at your hill, you don't really have any stats or pictures to show of what the event will be like and a lot of companies probably won't care. You could hit everyone up, but IMO I'd wait for bigger sponsors till things get rolling so you aren't the guy that hits them up for everything. Because some of these companies get hit up a TON. Also the ski shops in your area, are in your area. They deal with the same kids coming to the rail jam. Talk to them about throwing them on the flyer, getting some banners to put out on the course, things like that so they know they'll be getting exposure. Tag them in facebook posts about the event, throw them in the edit if you make a recap edit. If they're hooking it up fat maybe name them in the event. "Billy Bob's Ski and Snowboard Rail Jam" or whatever. Figure out how many prizes you need, so they have an idea when you first talk to them and you can make a solid plan. Most shops are pretty chill, so you should be alright. Ask for stickers as well. That's little and cheap but kids love stickers, and shops have a lot of them generally. Gives you something to toss out in addition to your prizes for people who just came out but didn't win anything.
When building the setup make it clean. Don't put a rail in an hour before the contest and be scrambling. The rail might not set and be wobbly, also a shitty setup with shitty takeoffs is no bueno. If you can build it the day before and finish it a few hours before that's best. Even if there's still little handwork, getting your rails set, and your takeoffs done early is crucial. They need time to set. Nobody likes a rail jam where the takeoff is loosely packed powder and blows out with huge ruts after 2 hits.
Give yourself proper time. If you can do it the day/night before that's best, things will set up over night, and you can do some touch ups the next day/focus on other things.
See if your mountain has a portable PA system or if you can borrow one from somewhere. A good go to is dub/reggae. Not many lyrics, and nothing really offensive, but good music for the crowd and people riding. If you have a PA, make sure who ever is playing the music isn't an idiot. If you have people complain about the music, you might not be able to have tunes at your next event. Or if you're playing Tswift, riders might not come back.
If you can get your hands on a megaphone that's pretty clutch so you can yell what the hells going on, that you're starting the riders meeting, that there's only 1-5 min left in the comp, or that it's done. Mention where prizes will be handed out and what time.
If you can get a few clip board. Grab some extra pens, and print off a bunch of copies of your riders list so you can score people.
Pick some judges that are at least competent regarding park so that a grab off the side of a take off doesn't beat out a switch lip on a rail.
Idk, I suck at organizing thoughts in these posts but I think I got it all. This is all just me though, so take what you want from this and light the rest on fire.
Best of luck OP!
TAKE PICTURES. If you have friends that edit maybe get one of them a free ticket to ski for the day to film some of the contest and make a good edit. Having good pictures and a good edit will make people more likely to attend your next event, help you promote said evvent, and get your sponsors stoked as well as making it easier to show sponsors a rough idea of what your events look like when you're planning future stuff.
Go crush it!
Have fun, and drink a beer!
Unless you're 12. Then just smoke a blunt, and drink some smirnoff or something.
"The mountains are calling and I must go."
- John Muir