I guess I'm going to disagree with the others as my opinion is:
Read as much as you need to. When you are happy with the ideas you've developed for a story, stop reading and start writing.
My stance may be a little controversial, but it suits me fine. When I read a lot, I find that it strongly steers my writing and my imagination.
If I read a book with a great romance, I'm easily tempted to put a romance into one of my stories. When I read yet another terrible fantasy book then I want to take my story and plonk it into a modern or sci-fi setting (which is actually what I did).
I have to limit the amount that I read or else I'd never finish a book. Worse, I could finish writing a book that ends up being a mish-mash of ideas I've accumulated from my reading. I would hate to finish a novel only for it to be extremely derivative, and everything feels derivative to me when I read widely.
Building upon the previous advice:
Take inspiration from sources outside literature.
A single lyric from a song is often enough to spark my imagination into overdrive. Sometimes it can be the view out of my window, or something I've seen in the news. Personally, I find non-written media to be far more valuable as sources of inspiration.
Disclaimer: These are techniques that work for me but obviously YMMV. Reading widely is generally recommended for the more disciplined author.