Anatomy of a Campaign Frame

Successful campaigns are woolly and difficult things to nail down. I have ran far more games than I've played, leaning towards a collaborative style with plots that the players care about but don't care about the players.  Cobbled together, cooperative Frankenstein constructs where every participant, player or GM, adds a little something (Nate dragged up a permissible torso, Larissa found a heart in the cupboard, Cameron thinks two livers would be grand, Rick had a plethora of toes, Carol dredged up a washboard for abs, Jeremy thinks making a centaur would be cool, etc.) Outside of Actual Play, when the dice hit the table, the most important way to stoke excitement is the pitch and how you frame it.  When putting together a campaign frame I like to brainstorm answers to three core questions: who are the player characters, what do they do, and what else is going on? 

The first question has variable answers, choices available depend on the game and which characters are picked (ex: in Apocalypse World - if someone picks the Chopper, then pack hierarchy is intrinsic.  In D&D 5e - if there aren't any outdoorsy types then the group are obviously NOT campers.)  You can often pencil this in if you know who your players are, players tend to cover specific facets of play (ex: I'm usually a barbarian.) If you're into niche protection then hold character creation with all of your players as an episode 0, so everyone knows what is being brought to the table.  If you aren't sure who's playing then keep it vague. This is where you start laying pipe to answer the second question, if this is a game where the characters are post-apocalyptic survivors, mecha pilots, hillbilly cannibals, super powered police investigators, or high school students then you need to cover that now.

The second addresses the core activity of the campaign and what the characters will be doing.  Look to inspirational media in a shared vein and crib from that (ex: In Supernatural - you're a family unit roving back roads and small towns of Americana killing monsters. In The Shield - You're all a group of dirty cops, balancing your responsibility to the unit and your civilian life.) This where you meet the players halfway and lay plot hooks for them. I like to hold character creation with everyone as a group and bounce hooks off my players and see what gets a strong, positive reaction.  This is a prime opportunity for your group to hash out what narratives you're interested in pursuing, if your players want to participate in a Battle of the Bands then incorporate it.  If you're leaning towards creating a world that doesn't revolve around your PCs, or the genre isn't familiar to your players, then you may want to jot up some plot devices/story hooks and just kick them out.  Make a table and have them roll on it, so there's a sense of input.

The  third topic you have direct control over, as it relates to macroplots (or metaplot,) campaign setting and backstage boogaloo.  Remember that no game prep survives the PCs, so don't over invest your time and energy.  Just provide clues and glimpses of what's behind the curtain to entice the players' imaginations (ex: In Max's Minions we've been manipulated by a wizard and now we want answers.  In the Adventure Zone our heroes have seen hints that the Bureau they work for has ulterior motives.  In Masks of Nyarlathotep, being a good friend of Jackson Elias is dangerous to your health.) Actual Play is where this pays off as you sustain player buy-in by building sympathy for NPCs, mildly frustrating players' schemes, and incorporating nearly everything that players put forth.  If a character has an entrepreneurial slant and he opens a pawn shop, then great.  Burn it down later, after he cares about it or not.  That's future you's choice.

After you've identified these bits of info you should be able to make a madlib that goes like this:
In (campaign name) you are (who are the player characters) who (what they do) but/and (what else is going on.)

Some examples from my previous posts:

In Wicked West you are occult prospectors who exploit the Otherworlds and introduce them to the power of gun.  Your greed and opportunistic actions poison the Tree of Life, and worst of all you aren't alone.

 In Habrá Sangre you are luchadores who fight for pride, tradition, honor, and the Gold  But the future, and your livelihood, is at stake so don your tights, pull on your mask, run the ropes and piledriver you opponents for glory.  Because in the end, this could be your last show.

In Kismet you are the flower of a romanticized age of Araby; visit the greatest cities of any age, defend your homeland, woo romantic companions, dare to engage in sword fights amidst pitiless dunes, and scribe your deeds on the Firmament.  Beware prideful ways, hubris lays low even the greatest among us.

In The Condor you are a crew of colonial criminals of conscience engaged in a global felonious fight against the impudent Imperial powers of Europa.  As in all Ruritanian romances of fighting trim, everyone knows someone of import and your actions may stoke the fires of a Great War.

This is the method to my madness, what works for you?