Just about every cat owner needs to use a cat carrier at some point. The reasons are many: moving, going to the vet, brining the cat to a boarder, etc. It is never a good idea to travel with an uncontained cat, no matter how well-behaved the cat is. 

You may become overwhelmed by the selection of cat carriers available. They come is many qualities, for example, you can get a very cheap cat carrier which is made from cardboard, or you can get a very expensive cat carrier which is climate controlled. The ones made from cardboard are only supposed to be used one time. Often, they are used to bring home a kitten from a breeder or shelter. Big cats will be too heavy for the cardboard and might claw or chew through it. 

You don't need to spend big bucks to get the best cat carrier. In fact, for most people, a moderately priced, plastic cat carrier is often the best choice. Often, these are made quite well and can easily carry a large cat of more than 15lbs. You will also want one which is easy to carry and will not hurt your hands while carrying. The hardest choice you will have to make is whether you wish to purchase a hard carrier or a soft carrier. 

In the case that you are physically carrying the crate for some time, you may wish to buy one that has wheels. This sort of works like a rolling suitcase. If you are traveling by air, then I must recommend a climate controlled carrier. The cargo holds where cats are often stored do not have heat and can get extremely cold during flight. A climate controlled carrier will make sure that your cat is cozy the entire way. These are much more expensive than regular ones, but cats have frozen to death in cargo holds, so I would argue that it is well worth the cost. 

For very long trips, you will want to make sure that the carrier has a place for food and water bowls. This way the cat can eat and drink when it needs to. You may also wish to line the carrier with a puppy wee-wee pad. This way if the kitty needs to use the bathroom, it doesn't make too much of a mess. I like to put an old towel or blanket in the carrier as well, this helps the cat stay warm and it is also comforting.