I leave the carrier in the room for awhile and give them treats, praise and pets when they approach or go in. I also put their fav blankets and toys in and give treats as traveling with soft music and lots of praise. The vets sometimes have cardboard carriers too. I would leave the carrier out after the vet and put a blanket on it cuz they may want to sit on it and getting used to it with treats may make the next excursion to the vet easier. Hope it goes great.