Some of these are contentious points with some people, but work for me.
Find out what they are interested in. Look at what they pay attention to in a session. Work out ways to either connect those things to the plot you have, or write some new stuff.
Talk to them after a session, too, find out what they're planning. If they won't say for fear of you foiling it, you have a problem that goes beyond your plot hooks.
Got a quest? Got a cool NPC to introduce it? Remember, the NPC only exists when the players know he does. There's no reason he can't change to fit the game. So what if they don't head North to Palestown, you can shift Palestown events to the town they're in.
Leverage your PCs backgrounds. You can have something happen to people they mention, have letters turn up from old friends, or old rivals.
The Time Warp
You are a storyteller, not a chronicler. You can always do a scene about things that happened earlier (heck, with some practice doing future scenes can be fun).
Let them do the Work
But tell them first. The players probably want to wander about bored about as much as you want them to. If you ask who's family crest is on the dagger, they can give a response. You may need to refluff some bits, but it can lead to really good plot. I find, though, that you have to explicit that they have permission to do this.
Show, don't tell
Don't tell them monsters are attacking. Have them attack. Even if it's in the distance, it engages the characters.
In a similar vein (which way require a lot of prep, depending on system) you can give them a set of different characters, who then get into a situation they can't get out of. The players tend to engage with this well, for instance "getting even" for a lost combat.
The Last Bit
All these techniques work with the player's buy-in. If they want to tell a story, let them know some of the techniques you'll be using, and that they have a part to play as well. You shouldn't be there to provide player motivation (character motivation, there's an argument), and they should be working with you to create something awesome.
You can't be expected to write an entire world.
You can however write enough for them to interact with.