But enough about me and my problems. Let's talk about your problems. To be more exact, let's talk about the people who are causing problems for your characters.
The technical term for this person is the antagonist. He, she, or it is the entity that's opposing your hero or heroine. Simply put, it's the bad guy. There are cases where the antagonist is actually the good guy in the story, or at least the more respectable one, but those tend to be much larger, Shakespearean-level stories (well, when they're done right) than anything most of us are dealing with. There are also cases where the antagonist and the villain are two separate characters (yes, it can happen-- look at The Fugitive). So for ease of discussion, I'm just going to be tossing stuff out with the understanding that the antagonist is the bad guy for whatever story we're working on.
(That title's another pop-culture reference, by the way, but only the older geeks will get it...)
The bad guy can make or break your story. Whether it's an enemy general, a high school mean girl, a homicidal sociopath, or even just the overbearing boss at the office, the bad guy has to be just as solid and well developed as your main character. How many books have you read or movies have you seen which failed because the villain was just a two-dimensional caricature tossing out random challenges and "threatening" lines.
So, a few things to keep in mind when crafting your antagonist. Like most things I toss out, they're not all hard-fast rules, but I think if you look back over some of your favorite books and films, you'll see that the most memorable bad guys tend to be...
Smart -- No one's saying the bad guy has to have a degree from Oxford, but if you've got a gullible character who has trouble opening closet doors and can't string two thoughts together, it's going to be tough convincing your audience he or she somehow rose to the position of being a real threat. There's book smart, street smart, and even just plain old animal instinct. But the reader has to believe your bad guy has a brain in his or her head. Remember, few things are more intimidating than a villain who's a step ahead of the hero--especially when that puts him or her a few steps ahead of the audience, too. In Die Hard, when Hans Gruber quickly assumes the identity of a cowering hostage, we all think John McClane is smart for asking his name and department... until we realize Hans assumed this would happen and already memorized the office directories.
Motivated -- The hero has a believable motivation, and the bad guy should, too. There has to be a reason they're doing whatever it is they're doing. Robbing homes, starting wars, humiliating people, killing kids at a summer camp-- none of these things are done just for the heck of it. In fact, one of the worst motivations a character can have is "just because," which is probably the only thing worse that saying "because he's insane!!" If the writer knows why these acts are happening, it helps flesh out the bad guy and make him or her more than a forgettable cut-out. The men who betray Edmond Dantes in The Count of Monte Cristo all have different reasons for screwing him over, but every one of them has a solid motive for sending their friend off to prison.
The Good Guy - This one's definitely not hard/fast, but it's an important one to consider, especially when you look at the last one. Many of the best villains honestly think they're doing the right thing, so their motivation is similar to the hero's (even if their methods are a bit questionable). Magneto in X-Men saw one of his subsets of humanity (the Jews) almost exterminated in World War II, and so he's determined not to let that happen to the other subset he belongs to (the mutants). The flipside of that is Josef Mengele in The Boys From Brazil, who honestly believes what he's been doing is the right thing, even though pretty much every historian on the planet would disagree.
Doesn't act like the bad guy -- It's easy to make someone the obvious bad guy. How many romantic comedies have you seen where the love interest starts off paired up with some who is so obviously not right for them? It's easy to have the third leg of that romantic triangle be a jerk or a bitch. When the bad guy straddles that gray line, they're a lot harder to write off. They also tend to be much creepier, because once their true nature is revealed it becomes clear how manipulative this character is. Consider Nazi Colonel Landa in Tarantino's recent Inglorious Basterds. He's a pleasant, polite, smiling goof who laughs at every joke...and yet the audience can't help but be on edge around him because of it, wondering when and if the other shoe's going to drop.
Calm - again not a hard fast rule, but like I was just saying, the quiet, friendly villain is almost always scarier than the shrieking, raging one. Just like with heroes, someone who's calm is in complete control of the situation. Part of the eeriness of the original Jason Vorhees was he was slow and quiet. Never rushed, never crazed. Who was really scarier in the original Star Wars-- Darth Vader who psychokinetically strangles a guy? Or Grand Moff Tarkin, who blackmails the princess with the life of a whole planet... and then coldly wipes it out anyway after she cooperates? And didn't Vader jump up a few creepy notches in Empire Strikes Back when he calmly invited the heroes to join him at the dinner table? Heck, consider that when we first meet Hannibal Lecter in Silence of the Lambs (either the book or the film) he's meticulously pleasant, doesn't make one threat, doesn't raise his voice... and leaves us squirming in our seats.
Limited -- When I talked about superpowers a few weeks back, I mentioned that the more believable tales tended to involve characters with limits. An all-powerful antagonist is just as boring as an all-powerful hero. Superiors, vulnerabilities, emotional weaknesses-- there has to be something that convinces people from early on that the antagonist can be overcome. Every tyrannical office manager has to answer to a supervisor, who has to answer to a junior executive, who has to answer to a senior executive. Captain Barbossa had a few unlucky gold coins. Randall Flagg is nightmarishly powerful in The Stand, but most of his power stems from people believing he's nightmarishly powerful. Bad guys need their own swords hanging over their heads.
Finally, one or two things to avoid. First, you don't want your bad guy to be a dupe. It's almost always frustrating on some level to get to the end and find out the bad guy has been blackmailed/ brainwashed/ manipulated into the role of the bad guy. If you saw the recent G.I.Joe film, you probably remember how silly and pointless it felt when it was revealed the Baroness was really a good woman who'd been hypnotized by... nanotech... or something. Not saying it's impossible to make this little twist work, but it has to be played with carefully because it's one of those elements that bad writers have pushed to the edge and now it's teetering on cliché.
Also, you probably don't want your bad guy to have some secret, hidden past ties to your hero. Ever since we found out Darth Vader was Luke's father (and I would apologize for the spoilers but come on! Where have you been?) it's been an easy out for writers to drop in this sort of thing as a weak attempt to flesh out characters. Janie and Megan were best friends back in grade school. Dillon and Dutch served in the same military unit. Jake and Mitch used to be in love with the same woman. These sort of reveals seem clever at first glance, but more often than not they're pointless and have no real bearing on the actual story. If you've got some of these ties in your manuscript, try cutting them out and see now much they really affect the story. If you've got less than ten lines of rewrites to do after removing them, you probably didn't need them.
And there you have it. Whether your bad guy is a bionic ninja warlord from the future bent on conquering the Earth or just Britta from fifth period English who wants to be prom queen no matter what, hopefully something in this little rant will strike a chord with you, one way or another.
Next week--and it will be next week, I promise--I'd like to rant a little about your backside. It's getting a little sizeable, and not in that good way...
Until then, go write. Go! Who's stopping you?