Let the players do some of the heavy lifting. No matter the setting or story, there are two things you can do to make your life easier as a DM and at the same bring your players deeper into the story:
1) Hooks
When you talk about hooks, I'd suggest going the personal route. Each character should have a personal tie to what's going on. Something not necessarily known by the other characters (but I recommend staying away from hooks that put the characters at opposition unless you and your players are very skilled, don't take things personally, and are ALL interested in such a campaign). The easiest way to get this going and draw in the player is to have each character write up a back story with one to three elements. Emotional elements (something that ties the character to one or more people, places, or things) and mystery elements (an event that had a true impact on the character that has some kind of unknown to it) are the most useful.
EXAMPLE: "My name is Loric, and I am the son of a local bartender. I grew up in this bar, where my father taught me the trade along with a tolerance for drunken patrons. While my parents fought on occasion, as most couples do, this weekend was different. The shouting rattled the windows and the sounds of splintering wood caused great concern amongst myself and my two sisters. The next morning, everything seemed back to normal, but that evening the strangers came. A man roughly the age of my father came to the bar with his daughter - an unusual thing, even for this sometimes seedy place. The man ordered a Scarlet Nip - no kind of drink I had ever heard of, but father seemed to take something from the words, nodded, and went into the back room. My mother came out and escorted the girl away. Late that evening, there was another argument as loud as the one before. Again, the crashing and shouting came, but this time it stopped all at once and my father snuck into my room. He drug behind him a large two-handed sword - the one he had always kept behind the bar. The one I would sneak out and swing around when he wasn't looking - back when I still wanted to be like him. This evening he handed me the sword, coated in blood.
"Take this," he said to me, "and head to Crystalmir. You must hurry." There was urgency in his voice and tears in his eyes. A noise came from the room behind us. He turned for a quick glance, then his eyes moved straight back to me. "To Crystalmir - the city is about 8 days southwest by horse." He dropped a bag of silver in my hand. "Look for a tavern there called the Swinging Dragon. Find the barkeep and tell him you are Kethirian. If he doubts you, show him the blade." A crash came from outside the window and another from down the hall. "Hurry," he said, "I... we will meet you there soon."
My name is Kethirian. Ten years have past, and I still work in a tavern. This eve, a stranger and his daughter come to the counter. I pull the sword I've kept all these years from under the bar, and I know I may not return. Not without my sisters.
Only three short paragraphs which give the DM several things to play off of. Here are 7, just to name a few:
1. What happened to his parents?
2. Why did he have to flee?
3. Who were the strangers coming to the inn? Are the new strangers the same as the old ones?
4. Who is Kethirian and why did his father hide his original name?
5. He used to look up to his father, but now... he's not so sure what to make of him.
6. He longs to see his family again.
7. The sword is some kind heirloom (possibly magical) and a symbol of his father and his family.
Now when you need a previously unknown NPC leader of the bad guys (the daughter of the man who came to the tavern), a victim of an evil necromancer (Kethirian's twin sisters), and punishment for getting caught and imprisoned (the bbeg, corrupt mayor, etc. takes his father's sword), you can reach into the player-written backgrounds. Not only does it make your job a little easier, but the players will feel much more motivated as they themselves have created some of the cast and the motivations themselves.
2) Plot Twists
Coming up with a good plot is hard enough. Coming up with compelling plot twists is often even more difficult. If you don't have a real gift for such things, or are just going through a dry spell, try tapping into your players again. Take your zombies, humanoids, or whatever and have them do something that otherwise doesn't make much sense. They assault the village, then suddenly stop. Have the players discover something out of the ordinary. They finally make it into the den of the beasts and discover a giant black orb. It is cold to the touch, and gelatinous, though you can't seem to pull any part of it away from the whole. Every 7 minutes it makes a humming noise for 7 seconds. Have them come into contact with mysterious people. As they enter into the temple to pray during the weekly services, they notice a man in white satin robes leaving the priest's chambers. His robes have two crescent moons reflected upon each other on his chest, embroidered in gold. As he leaves, he nods in the direction of one of the player characters (pick one at random or one where this character might fit into their back story), then heads out. When the priest enters the main hall for services, he is visibly sweaty and appears nervous. He will not reveal anything to the players at this time.
So, why did the creatures stop attacking the town? What is that black orb? Who was the man leaving the private rooms in the temple? You don't have to know yet. You can attach some of these things to the character back stories. You can figure it out later as you go. Best yet is that you can listen to your players. If they're into the story, they'll be tossing about their own ideas. Listen carefully and you'll probably hear some really interesting possibilities that you can bend into a real story.