First off, read as many of the classics of magic as you can. Tarbell, Erdnase, Royal Road, Expert Card Technique, Sachs' Sleight of Hand, Martin Gardner's Encyclopedia of Impromptu Magic, Bobo, The Amateur Magician's Handbook, etc. As well as giving you a good broad overview of what's gone before, you may well find ideas for plots and methods that spark your creativity.
Next, sign up to askalexander.com. This is, quite simply, the best magic resource the wit of man has yet produced. I believe that, at the top subscription level, there are now well over a million searchable pages of text, including complete runs of many magic magazines, all of Max Maven's books, all of Harry Lorayne's books, hundreds of pre-20th century books, and the list goes on.
Also, network. Get in touch with knowledgable magicians, privately show them your idea and see what they have to say. One of the handy things about magic is that even those who are very well-known in our community aren't huge celebrities who have five levels of management to get through, it's normally very easy to get in touch with people directly.