I try not to railroad -- sometimes I'm more of a plot-commie than a plot Nazi. Y'know, from each according to his ability....
For example, the players might be traveling through a city, and they're afraid they're being followed. A PC native to the city asks, "Do I know of any quiet teahouses nearby, maybe with a back room?"
I'll look back at the player and say, "I don't know. Do you?"
At which point she'll grin and say, "Yeah -- about two blocks from here, the Silken Mug. It's pretty posh, but the owner, an elderly elvish man, is very discreet."
And I'll say, "Fine," and they go there, and I take on the role of the elderly elvish man that she just told me about, and the adventure continues.
On the other hand, I throw hooks at PCs with the understanding that they'll do something with the hook. If they learn about a ghoul-worshipping cult in town, they need to blackmail the cult leaders, or go guns-a-blazing into the cult temple, or they need to infiltrate the cult, or they need even to talk to the authorities about the cult -- but if they completely ignore the cult, I'll be peeved.
One other thing: when I'm lazy, my plot hooks come across as wild coincidences (a PC's husband happens to be a member of the cult, or the PCs just happen to be 100 feet away from a fight when it begins, or something like that). The PCs, for some reason highly suspicious of the world in which they live, have a hard time accepting that anything is a coincidence, and are convinced that there's enemy intent behind everything (is the fight down the street a setup by their enemies, designed to get them into trouble with the law?)
So how about y'all: are your plot hooks often wildly improbable, or do you try to make them subtler and thereby less coincidental?
Daniel