Gaaah!
Wow, I must suck then. I'm the antithesis of preparation. I've always found it useless. The few times I've tried it, it's DOA (excepting exactly 3 occasions). And when I abandon it, I'm rewarded.
I go for a little more of a movie feel. Watch a lot of movies, know the rules, get the nugget of a plot, make some badass NPC's and get ready to rumble.
Getting players to follow whatever story I think I have mapped out has always been like herding cats. They're gonna do what they're gonna do, and careful preparation will probably get shot to poop before they roll the opening credits. So I go with something more...dependable. Motivations. NPC's are my characters, typically the Players play the heroes, but I get to play the villains, the wild card, the day players and the crowd. If the NPC's wander, the motivations of the villains will pull them back in, or the wild cards needs will change their path, or they won't in which case it's time for a cool spontaneous sub-plot. It just makes it way easier. Play *your* characters, the players play theirs and the story writes itself. Almost.
You can be a Shakespearean role-player. No, you don't have to speak in iambic pentamiter, wear tights, or die in a tragically ironic gaming accident. Remember what interesting, funny, cool, or just (by any measure) noteworthy, things the players did, and when an opportunity presents itself to have one of those things brought back up, do so.
Other movie-isms, establish your villains. That opening sequence where they throw down unholy hellfire unto their hapless victims and disappear, yeah, they need one. This is easy. The bad guys have the gear, the know how, the plan, and most importantly, the element of surprise. The PC's, can monkey with it, and maybe take down some henchmen to stroke their egos, but the out come was never in doubt. Remember your Sun-Tzu, it's not the best warrior, it's he who chooses when, where, and how to fight best.
Everyone loves the underdog. Therefore, PC's should be the underdog. Don't be afraid of sending the PC's into the lions teeth against a foe who on a level playing field could never loose. If you don't know how they can win, that's their problem

. And when they do, it will be that much cooler.
Deus Ex Simian, aka the monkey with the wrench. Every good story has twists, one way to do this is with an NPC, who has similar but different interests as the PC's. You could do this almost any way I suppose, perhaps even diametrically opposed. This could be a love interest, a more dramatic version of a caravan I suppose, the buddy with or without problems, who may or may not be reliable, or any number of the thousand variations one sees. Work them up like they were a character. What do they want? Who do they think they are? Where do they fit in? Why do the do that voodoo that they do so well? How much do they know? If you know the answers to those questions, then the players can't send you somewhere you're not prepared to go.
Man Up. Luck Favors the Bold. And if the PC's know this, they'll probably choose the moment of your climax at least as much as you will. But, to a large part you control the setting. So if I was going to plan a lot, this is what I'd plan. Not with painstaking maps, and all kinds of obscure details I could never use. But I would want a very clear, firm image of what it would be like, look, smell, sound, feel etc. When the time comes, feel it out, does it feel like Clint Eastwood in the old west? A mexican standoff? The end of Empire Strikes Back?
But how to get the player(s) to take the bait? Not that every adventure shouldn't start with the PC's walking into a quaint tavern where a withered old man in a robe asks, "Want to make a few gold pieces?", but...well...they really shouldn't. Just figure out what kind of bait the PC's want to take. Don't be worry if you have to try a few lures out, sometimes it is more about drinking beer than ending a day with entrails in your hand. (I'm talking to you Tony, and I'm not just talking about fishing.)
You can lead a player to danger but you can't make him think. If they do something that would get them killed, injured, or possibly deported, don't hold back. Sometimes this can be the cool opening scene that establishes the villain for the character they've just started rolling up. Sometimes it ends up on the "How Not To Be A Superhero" instructional video. (Can I get an amen for my brother with the shoe box of pictures?)