The site Info Red posted is indeed a great spot to begin with and I too can vouch for Tarja's generosity...she has helped me immensely the past few years.
I have been doing solargraphs for the past 5 years so can answer just about any question you might have about them too.
My best tips are to make sure you put them in a place that can remain undisturbed for a long period of time.
Rain, snow, and minute peices of debris can work its way into the camera, but it's all part of the final product.
It's really simple and very rewarding in that you truly have to rely on the Sun to make its marks on the photo paper.
Have fun, and if you have any questions, ask away..
Becky