Line the bottom of the container with absorbent material, eg newspaper in case your cat needs to urinate or water is spilt. Cover this with a familiar smelling blanket (or piece of your old clothing) so that your cat can rest in comfort. There should be a dish of water and dried food may sometimes be useful on a lengthy journey. If your cat has a favourite toy, put that in its carrying box. If your cat has not been in the carrying box before introduce it well before the journey. Leave the box around the house for a few days with the door open and a blanket inside and your cat will probably go in to explore. Spraying the inside with a pheromone (natural cat scent) before travelling may make your cat more relaxed on your journey. Once your cat is used to the container, feed it inside there and shut it in for short periods before travelling.