I remember the first show I did, I bought a VHS video tape called 'perfect posing'! I had never been to a show or seen anything on how to pose or anything of the sort. The videos helped me tremendously at the time! lol, looking back on it now its kinda funny as there is so much more information out there on the net now that is free and 100x better then my little vhs tape. As someone else said here, its better to have some experienced help from someone that has been there and done it, but if you don't have access to that a book or tape in my case will do just fine!
that chris aceto book is good. Theres a few others i remember reading and using back in the day as well, I can't remember them off the top of my head though.
Theres a ton of info on this forum if you have the time to look through things. As some others said, getting a coach or someone to help is the ideal situation. I know a lot of the coaches and prep companies will give you some very basic info for cheap too.
The only thing I don't like about buying a book if that you tend to think the info in it is the be all end all ( at least i did when I was young) and things have changed SO much since then! if you can get a coach to help you that is willing to take the time to learn your body, that would be best.