I went to a few shows with a neighbour and helped him show his sheep to get an idea, and then to prepare my sheep which were a different breed I got in touch with a local breeder and she very kindly showed me how to card and clip etc! You will find that most people are very encouraging and helpful. I loved going to the shows, I had a lot of fun and won a few prizes too!
As for shearing, you do it early so that they have a good fleece on them by the time you hit the shows. There is a lot of primping that goes into preparing the sheep. Shampoos, brushing, clipping etc! All a lot of fun! The basics you will need are a good carding brush, sharp shears and a paddle.
The main thing is to have fun and not be afraid to ask questions at the shows