I love writing for the YA age group - one of the great things about the age range for YA is that is is ever-expanding. It is not set at just young adults but reaches right up the scale.
The Twilight series and the works of Philip Pullman (for example) gain such big readerships and go on to further influence other writers too.
The supernatural YA genre is my particular favourite to write in - I love supernatural as a subject matter (it's so very wide in scope) and I can relate to all ages of reader - (we are all children / Young Adults at heart really, we don't grow up - well, not too much).
My tip for this genre is to write not just one book but a whole series.
This is not only because a series might attract a publisher much quicker, but because once you have written the one book, you won't want to stop. My suggestion is that you read one (or more) of the series that Darren Shan has written. His writing is spot-on and superb.
Here are my Top Writing Tips for this genre:
Vampire culture - you don't have to stick with what has been tried and tested, make up your own worlds/characters and hierarchy.
Spirit World - create a new way of the Spiritual Realm coming through to ours: i.e. portals.
Superstitions - different countries of the world have their own superstitions, explore these and perhaps bring a twist to them.
Shapeshifters - how many different ways can you introduce this belief into your story or book - maybe even write a book about different types of shapeshifter - or an alternate world where only they live.
Real world - can you take a normal, everyday routine from our world and make it into one that's tinged by the supernatural? Maybe have spectral school bus drivers, who veer off the normal school route for naughty children, or a ghost town that comes back to life only one night every year - and it traps some of your characters. How will they escape?