I think I've said it before, but I do think one of the best ways of improving your writing is to read a lot. And then read more. And then go to the library and read some more.
One of the things I like to do is check out the #FridayReads hashtag on Twitter*. You get a huge variety of ideas from other people's suggestions. A lot of them might be things you don't fancy, but every now and then something will catch your eye that proves to be a real gem.
So what am I reading at the moment? Well I just finished a Star Trek YA book called The Edge (good read, nice plot, and easy to settle down with), I'm in the middle of an intriguing historical mystery Death of a Dancer by Caro Peacock (great descriptions of Victorian London and good characterisations), and my pile of books to read includes a fantasy, a Christian romance, local history and a diary-style how-to guide.
* On Twitter you can flag up certain subjects, talking points, ideas, etc, by using the #. Every Friday lots of people will pick a book and tweet about it, adding #FridayReads to their message. Other people can then search for the list of messages with book recommendations by searching for #FridayReads.