Start by reading the saddle fitting threads here, measuring your sitbones, and deciding whether you need a cut-out or not. *Then* go to your LBS and see about trying saddles that fit your general requirements. There's a lot of trial and error, but it's no different from trying on clothes, that way. If you know your size and general shape, you can narrow the choices quite a bit. If you don't, you're almost guaranteed a lot of frustration.