When choosing a cat breed, especially as a companion animal, you need to consider coat type. The type of coat your coat has will determine how much it sheds and how often you will have to groom your coat.
The hairs on a cat grow from tiny pits in the skin called follicles. Primary hairs, also called guard hairs, are the longest ones in a cat's coat. These grow from individual follicles. These are the hairs that lie on top of the coat and may be either soft of bristly, depending on the breed. These hairs are found on most cats (with the exception of the 'hairless' variety).
Secondary hairs come in two types. Awn hairs are bristly tipped and about medium in length. Down hairs are fine, crinkled, and short in length. All secondary hairs grow in groups from single follicles, making them more likely to tangle and mat.
Grooming needs and shedding are primarily determined by coat type. Cats with a thick undercoats (which consist of secondary hairs) shed more and require more grooming. This is because secondary hair tend to mat and require more attention. So fluffy breeds with a soft undercoat such as the Persian, Himalayan, Balinese, or Birman will require more grooming. These cats have longer hair, but fluffy shorthaired cats shed just as much and need grooming as well.
Cats without the thick undercoat, including the Abyssinian, Siamese, and Oriental Shorthair, will still shed. You really can't avoid it. But they'll drop single hairs instead of large clumps of fuzz. These single hairs are easier to sweep off the couch and don't tend to embed themselves in carpets. These cats don't necessarily require regular grooming, but a quick brush once a week will at least cut down on those pesky hairballs.
Whatever cat you eventually choose, make sure you're aware of their grooming needs. You don't want a cat who's uncomfortable or unhealthy simply because you neglected to do your research.
Just taking a look at the various cat breeds quickly reveals one key difference between many breeds: the length of the coat. Most breeds are shorthaired, such as the American Shorthair, Bombay, Abyssinian, Manx, and so many more. Some are longhaired, such as the Cymric, Persian, and the Ragdoll. Then there are a few of the hairless variety, such as the Cornish Rex and the Sphynx. Coat length is a defining characteristic of many breeds.
In fact, for some breeds coat length is the defining characteristic. The Somali is the Abyssinian with longer hair, but they're not the only breeds separated only by the gene for coat length. In fact, there are six others. These breeds are: the Manx and the Cymric, the Oriental Shorthair and the Oriental Longhair, the Colorpoint Shorthair and the Javanese, the Exotic Shorthair and the Persian, the Scottish Fold and the Scottish Fold Longhair, and the Siamese and the Balinese. Take a look at pictures of the breeds and you'll just how similar they are. If a Somali was born with shorthair, it would pass for an Abyssinian. They're the same cats, just with a different coat length.
Coat length also relegates cats into shorthair or longhair speciality rings at shows, except in the Cat Fanciers' Association where speciality rings are determined by facial type and body conformation. On a practical level, coat length usually determines how much maintence and grooming is required. The Exotic Shorthair will require less grooming than the Persian. It's just a fact. And the hairless breeds require even less.
I talk about hairless breeds now and then, but the term 'hairless' is a bit of a misnomer. Most of the hairless cats are actually covered by a faint peach fuzz, making them shorthaired cats. Still, their hair is so short that if you're classifying cats by coat length, you really should have three categories. I know most associations don't (though there are some that do), but they should. Just my opinion.
So why is coat length important if you're not breeding or showing your cat? Gromming is an issue surely, but so is shedding. Both longhaired and shorthaired cats shed. Only a couple of breeds shed less, but all of them will drop some hair.
When choosing a cat breed as a companion animals, you'll have to consider how much grooming you want to do and how much hair you're willing to put up with. Choose your breed accordingly and save yourself some frustration. There's nothing like the sight of a beautifully-groomed Somali (or insert any longhaired breed here) walking across a sun-lit window sill, but if you're not going to do the grooming, or you're going to hate all the hair, you might want a shorthaired breed.
You might think that size wouldn't be a problem for cat fanciers or breeder. After all, most breeds of domestic cat are fairly uniform in size. Shouldn't this make creating new breeds easier? Doesn't it mean that you can cross breeds and experiement without having to consider size?
The answer to the second quesiton is yes. The answer to the first is, unfortunately, no. Unlike dog breeders, who are able to work with a wide variety of sizes, cat fanciers and breeders are very limited in design. The difference between the largest breed and the smallest breed is barely 12 pounds in weight and less than 1 foot in length. The diffference between the largest and shortest facial profiles is only 2 inches. This isn't a lot to work with in terms of developing new breeds.
This presents a problem for cat breeders that dog breeders simply do not face. If you have only one size to choose from, new breeds, or even variations on a single breed, are difficult to come by. Despite this limitation, breeders have managed to create more than fourty distinctive and recognized breeds. While this may not be as many as dog breeders have been able to create, it is still impressive given the limited variables cat fanciers have to work with.
The eyes are often said to be the windows to the soul, and the eyes of a cat gleam more than most. The romantic notion that a cat's eyes gleam because they house great power or are otherwise mystical in nature is pretty, but there's actually a very scientific explanation for the mysterious luster you found in a cat's eyes.
Cats are the most efficient gleaners of light. Their pupils can dilate to a full half-inch in width or narrow to an almost-invisible slit. Their eyes can take in as much or as little light as they require to effectively see. This trait allows them to see in almost complete darkness. Contrary to popular belief, they cannot see in absolute darkness; Even their sensitive eyes need some light to make sense of the environment. But they can see their surroundings in great detail with only the smallest bit of light.
Cats are not completely color blind, though they can see red only in the emotional sense. By which I mean red is outside their visual abilities. They also can't see orange, since orange is a combination of yellow and red. They can, however, see striking shades of blue, shades we will probably never be able to appreciate.
Felines are also a little farsighted. In fact, their depth of field is in sharpest focus between 7 and 20 feet. This is not to say that they cannot see things outside this field. They can, but they'll see it in sharper detail if it's inside that range.
When choosing a cat breed, especially as a companion animal, you need to consider coat type. The type of coat your coat has will determine how much it sheds and how often you will have to groom your coat. 
