Fighting the affliction of what is commonly called writers block is crucial to being productive. We've all sat staring at the computer screen not writing. How do we fight it to stay productive?
One technique is to write boiler plate--that is, write whatever comes to mind, even if it's crap. That can sometimes be enough to keep the momentum going. Occasionally, it turns out better then you expect and you wind up with something to sell. Other times, you just chuck it.
Better is research. That isn't necessarily online or in a book, but it could be. One of the exercises Orson Scott Card assigned during his writing class (the one open to everyone, not the bootcamp portion) is the index card exercise.
Basically, you write a story on one side of the index card using as few words as possible. Boil it down to the essentials. Five cards--five stories--are used. Two story ideas come from library research, two come from simple observation of everyday objects, and one comes from interviewing a stranger.
Of the 5 index card stories I wrote during the 2005 bootcamp, I fleshed out three and sold two. The one I didn't sell is really part of a novel that I will write down the road a piece.
It's a good exercise that teaches you the technique of generating ideas. That's what writers mean when they say ideas are everywhere. They are, you just need to know how to find them. Once you understand the process of generating ideas from whatever is around you, you start seeing ideas all around you.
Orson Scott Card also has another method that he calls "thousand ideas in an hour." I won't go into that because it's well documented in his book Characters and Viewpoints (highly recommended). It is a brainstorming technique created specifically for story generation.
To me, the "thousand ideas in an hour" is bringing out the big guns, when you just can't find a story idea any other way. It can be powerful, but I've never needed to use it to build a story from scratch because I don't generally have trouble coming up with ideas. I do sometimes use it to generate an aspect of a story I have in mind.