Fiction, non-fiction, prose, poetry, in and out of your preferred genres - ideas can spark from what you read so the more widely you cast your net, metaphorically speaking, the more likely it is you will "nab" something which you can develop and turn into your unique fiction.
I've found writing exercises to be phenomenally useful for developing the old imaginative muscle. I list three exercises below but there are many others.
- The Hemingway Six Word Story exercise. His classic was "For Sale. One pair baby shoes". A recent one of mine is "He refused to kill the dragon". I've since developed this into a flash fiction piece. But this is the great thing with this exercise. It effectively gives you an opening line and it is up to you what you then do with it - flash fiction, short story, poem, the beginnings of a novel, anything is possible.
- Write a closing line. Sometimes Writing Magazine offers this as one of their competitions. They give you a finishing line and you work out how you got to that point. I've not used this one much but can see the usefulness of it.
- Free writing. Set a time limit, say ten minutes, and literally just write anything. Switch off the inner editor and just go for it. The great thing about this one, which I use when I want to brainstorm future ideas, is I know whatever I come up with is going to be very rough and will need a lot of work but so what? It really doesn't matter and knowing that can be liberating. That in turn frees up your writing and your imagination and hey presto, on paper, you've suddenly got something you can work with. Even if you come up with five ideas and you dismiss most of them, for whatever reason, you will find something you can explore further. I've found in exploring an initial idea, other ideas follow. It can be the getting started that can be difficult at times but this exercise is a good way round that.