(I am quelling the desire to justify this, so that you don't think I have nothing to say and/or shouldn't be working in a creative field. Have I also just given too much away, admitting as I have that I care what you think? As this paragraph is bracketed, I would prefer if you never mentioned having read this. Thanks!)
If I sit there at my computer and think, 'OK, let's find something for my characters to do,' I will freeze, entirely. My characters will do nothing. They'll sit around an office, or a coffee shop, or a living room, wittily, insightfully, charmingly, gazing into their navels and remarking on the world around them (and this world will, probably, be quite a lot like mine). This kind of fiction is rarely of interest to people who read things. Honestly.
So, I have learned that, for me, I must come to the empty Word document with a hook or concept, lest I write yet another moody coming-of-age tale where nothing happens (which I love, by the way, and will never stop writing). You come up with these concepts by having things called ideas. These can be found all around, and when you get these ideas from around you, it is said that you are drawing inspiration.
Mur Lafferty wrote a good little blog post about ideas and generating them. Essentially, ideas are like a magic penny, hold it tight and you wont have any, but spend it, lend it, and you'll have so many that they'll roll all over the floor. Yes, I just stole those lyrics from a song about God, but I think it works in this regard too. Basically, you're supposed to use all your ideas all the time, and don't save them up for later. You'll think of new ones. Getting the old ones out of your head and onto the page will actually clear room for new ones. This is, I think, Science.
So, in summary, in order to be a good fiction writer, you need ideas. You may well have known that already. The good thing is, prompts for ideas are all around us because we live in a world where there are so many things! One of the first assignments in my masters course was to find a picture and write a story about it. I can't find the original picture, but I'm fairly sure that it was a Studio Ghibli film still with a little girl looking at her reflection in the river. So I wrote a terrible (not in terms of subject matter, in terms of quality) story about that!
It's a good exercise, because it teaches you not to be too precious about your subject matter, and to look deeply into everything around you. If you can create a story sparked by just one little picture, what can you do with a whole world at your disposal?! Write more stories, mostly.
Music is good for that. Just this week, I was very inspired by an Elbow song. I haven't yet turned it in to anything, but it made me want to write a poem for the first time in ages. I then realised, while trying to write the poem, that I had no idea how to write a poem and that copying song lyrics is not the way. However, the first short story I ever got published was based on a song by Air, called Le Voyage De Penelope. It wasn't so much the song as the title; and it was a very literal interpretation. If I tell you that the title of the story ended up being Le Voyage De Lady Penelope, I think you'll get a good idea of where I went with it. I still quite like that story though, which I almost never say, modest bastard that I am.
It doesn't always work. I was fascinated by the painting below for about ten years, I even made a sculpture of it, from wire and black feathers, and have, in my head, turned her into a superhero, but I have never been able to write something about her that isn't, well, a bit rubbish.
See also: the above Elbow anecdote. they can't all be winners!
Still, this is my advice to all those struggling for ideas: