Answer 1: Find roads. Sounds simple, but it's not. Going out and looking for them is fun, but doesn't usually yield a lot of productive results (maybe 30% of the roads you look at will be useable in the end, if you're lucky). I'd suggest starting with a County DOT, and seeing if they have a county Right of Way map. You may also want to talk to their special event permit coordinator, and explain what you want to do. You're going to get one of two initial reactions: (1) that sounds like fun, we'll need to think about whether we can allow that or (2) we don't allow that kind of thing around here. I've gotten both responses from counties that are adjacent to each other. If you get the latter, you've got your work cut out for you, and it's probably not worth your trouble (though I've personally got a plan to overcome that particular response, but it will take a few years). If you get the former, you need to be prepared to convince them that we are not just a bunch of irresponsible yahoos looking to tear up their roads. If you get that far, PM me and I'll send you a powerpoint presentation that you can tailor to your needs.
You might want to take a look at
www.geocommunicator.gov. Some of the map views will show you roads that have documented rights of way. I am not sure if they show these for roads in national forests, but they do show them for lots of BLM roads. Keep in mind that just because a road isn't shown as having a ROW doesn't mean that it's not a legal road, it can just be a little messy. If there's a documented right-of-way, you're in good shape if you can get a county permit. If not, it really depends on the particular situation between the county, the feds, private land owners, and perhaps the state. A friendly warning that you may become lost in bureaucratic hell, but don't let that dissuade you.
After you've got your list of legal roads, then you can pare it down by going and taking a look. Keep a lookout for places where you are going to block somebody in. That doesn't usually go over well. It's best to grease the skids with any affected landowners in person before doing all the permit paperwork. Sometimes, they will be friendly and willing to strike a deal. Sometimes they will, umm... not be.
There's a lot of variability here. The original road that we used for Desert Storm was a trivial to get permission for initially. However, it then got somewhat difficult (or impossible) for a few years, and is now back to a reasonable level. The roads I am working on for the Black Mountain Rally are insanely messy, but things are slowly starting to fall into place.
Answer 2: If you get response (1) above, you may not need to do this. Just find a place for your HQ, service area(s), etc, coordinate with the local emergency services, HAM clubs, and other organizations that need to know what you are doing. If you can run a viable event without promising anybody anything, you're better off in the long run, because there isn't any room for misinterpretation of those promises (i.e. they said there would be X number of hotel rooms sold, and there were only half that many). If the event doesn't annoy anyone in the community too much, and people see a benefit to the event (usually economic, but maybe just something to do on a particular weekend), you'll build goodwill in the local community, which can help you build the event in future years.
--
John