Cats should be taken for a check up at the very least once a year, but every six months if possible. A "well cat" visit is probably the most important thing for a cat's health. During this visit, your veterinarian will check the cat's body, looking for signs of diseases or anything unusual. Your vet will check your cat's ears for parasites, mouth for tartar and gum disease, heart and lungs, and skin for lesions or bumps. Your veterinarian will also weigh your cat and assign a body conditioning number (1-9). A high number means that you cat is overweight. Ideally, you want to be around 5 on the scale.
Outdoor cats are at a higher risk for disease, including viral and parasite infections. It is important to your cat's health to say up to date on vaccinations annually.
The best advice in taking your cat to the veterinarian is to start early. Take your cat for car rides as a kitten and you cat will get used to the carrier and riding in a car. Put toys and treats in the carrier to make your cat happy. The key is to build a relationship with your vet from the beginning. Focus on preventative care which can help keep your cat healthy for many years to come!