Are you new to running a tabletop RPG campaign? Let me give you a hand in doing this. Before you talk to players, you should sit down and work some things out first. Your campaign, done properly, is a sandbox that your players play within. It's not a stage, and therefore not a story. It's a sandbox because you define a space, and throw in some toys to use, then let the places loose to make of that as they will.
Some games make this easier than others, but what I'll talk about here (and in follow-up posts) will apply to any such RPG. The big difference will be in additional work meant to get it down to something manageable at the table. I'll walk you through the process, step by step; in writing this looks like a lot, but in practice it's not. You can handle all of this while watching TV after dinner on a weeknight, especially if you look things up during commercial breaks or between episodes of what you're binge-watching.
When I decide to run a tabletop RPG campaign, the first question I want to answer is this: "What will gameplay be like most of the time?" I need to know this because all of my decisions after this point will be informed by that answer; your effort is supposed to be focused on where the gameplay is, and not on irrelevant stuff. If your game is going to focus around exploring the wilderness and the dungeons found therein, you don't need to figuring out relationship maps between NPCs or political influence matrices. You don't need nails if you're going to do calligraphy.
This is where you find that game design first makes its quality known; the best designs have that front-and-center so you can just play that out of the box. Dungeons & Dragons, Traveller, Call of Cthulhu, and King Arthur Pendragon all have this. Others require more work out of you before you've got something like that, so let me show you how to navigate this also.
Palladium's RIFTS is one of the worst for this. The setting isn't a setting as such, but rather many big settings tied together by the concept of trans-dimensional travel (and all that institutionalized use thereof brings). To make a manageable tabletop campaign out of something that inclusive, you have to start splitting off elements until you get down to that easily-executed gameplay activity.
If there is a default in RIFTS, then it involves North America and the Coalition States. Either you're playing characters opposing it, or you're playing characters that support it. Playing actual Coalition military personnel is not unusual, so let's go with that.
The Coalition States has a large army, with a significant (but small) air force included. Its Navy is small, and despite pretensions is really just a glorified Coast Guard/River Patrol. What, among all of this, would be best to build a typical tabletop RPG campaign around? You want something that easily allows for players to not attend due to real-life issues and miss little or nothing, and you want something that's friendly to new players or replacement characters. Further, you want something that any player can grasp with the ease of D&D's dungeon-crawl default structure.
In this hypothetical instance, that means playing an infantry unit of some sort. Not the crew of a vehicle of any size, or pilots in a squadron, and not Special Forces. Ordinary line infantry, walking assigned patrols, dealing with what's encountered- be that expected or not. Given that North America is mostly a demon-haunted post-apocalyptic wilderness, you now have all that you need to put all of this down into a single High Concept pitch:
You play Coalition Army soldiers on patrol in the Magic Zone, enforcing Coalition law on its most dangerous frontier,
and making the land safe for future settlement by Coalition citizens.
Now we have a default gameplay structure. We can pull out books, films, etc. on Vietnam, Afghanistan, Iraq, and other post-WW2 wars where this sort of operation is standard. We can also incorporate older examples as they show relevance, and from them we can start putting together go-to patrol missions, likely encounters, and all the other stuff a proper campaign requires to keep a game going early on before the players' deeds start driving events.
But wait, there are monsters and sorcerers to contend with. That means mining the wealth of horror stories involving rural settings (or easily used therein), from Howard's many tales featuring Solomon Kane, Conan, Bran Mac Morn (etc.) as well as Lovecraft and Derleth and so on (in addition to more contemporary takes). Then mix them together and you've got a good rough template for you to smooth out to suit your table.
Sounds like fun, eh? Fun to do, fun to run, and fun for players- that's when you know you've got a campaign ready for the next step. I'll talk about that next time.