Don't switch brands unless it's for a good reason. Cats are creatures of habit, and if they've been happily using a brand of cat litter they may not want to make the switch, even if you may find it messy or hard to clean.
Clumping litters are preferred by cats. Clumping cat litters, whether clay-based or biodegradable, react with urine to form hard lumps that can be scooped out and either flushed down the toilet (if the litter is biodegradable) or put in the garbage (if it's made of clay). Cats like the feel of most clumping litters, and experts say that clumping litters make it easiest to keep your litter box as sanitary as it can be.
Don't judge by price alone. Some clumping clay litters are relatively cheap, but they can be tracked across the house by your cat's paws. Resist the impulse to buy the cheapest litter available, at least until you've hit on the right combination of features for you and your cat.
Put your cat's comfort first. Feline paws are very sensitive, so a cat may or may not react well to the feel of certain litters, especially pellets or crystals. If you sense your cat is using the litter box under protest (lots of meowing and fussing around), switch to a type that's easier on its feet.
Are there young kittens in your household? Fine-grained cat litter might be what most cats prefer, but it isn't the best choice for kittens younger than 3 months old. This is because they can ingest the small particles, potentially causing illness.
Keep it clean. Expert after expert say the same thing: The best way to deal with odors is to follow a strict regimen of litter box maintenance. Clumping litters need to be scooped out twice daily, at a minimum. Though some litters (such as crystals) allow for longer intervals, in most cases plan on dumping out and cleaning a litter pan weekly. Wash the litter box with plain water, or use a fragrance-free soap.
Your cat is the final judge of which litter is best. Despite the best expert and user advice we can share, the final arbiter of which litter is best will be your feline friend. If you choose a litter that your cat can't stand, the end result could very well be a cat that won't use its litter pan. If your cat is happy with the litter it is using, be very cautious in changing things up. Cats are creatures of habit, and if they've been happily using a brand of cat litter, they may not want to make the switch -- no matter what your reason for making a change. With a new cat, experts suggest leaving out pans of different brands/types of litters so you can learn what it prefers.
It might not be the litter. While a cat might not be totally pleased with its litter, if it suddenly starts eliminating elsewhere, that could be a warning sign of a medical condition. A visit to the vet might be an important first step before experimenting with a different litter.