One important difference between an adult cat and a kitten is that adults have the potential to breed - and they will breed if left to their own devices. Unless you have a pedigreed cat which you wish to mate, it is always advisable to ensure that your cat is neutered before it reaches sexual maturity. Cats that are not neutered, especially males, also tend to roam and fight more, and males will spray their territory, both indoors and outdoors, with pungent urine.
Cat Proofing Your House
You should try to ensure that your house is 'cat proof' against accidents. Cats are rarely clumsy but they explore wherever they can. Any fragile items should be put well out of a cat's reach, ideally in a cabinet rather than on an open shelf. Cats may crawl up chimneys, jump on a stove, bite through the extension cords on appliances, or knock over hot irons left on ironing boards.
They may chew on a poisonous plant, crawl into a washing machine or dryer, or sit under a car - or, even worse, crawl beneath the hood from below and perch right next to the engine. Kittens and young cats are the most likely to get into trouble. Stop them going near any potential hazard with a sharp 'no!' and avoid tempting fate by closing doors, turning off appliances, and putting things away. Put screens on windows.
Cats, as well as kittens, require opportunities for games to prevent them from becoming bored and even destructive. If you are away from home for most of the day, it may be worth considering getting your cat a feline companion. A cat 'multi-gym' or activity center provides exercise as well as entertainment and is particularly beneficial for an indoor cat.
If you do not wish to keep your cat indoors all the time, a pet door is very useful to allow it to come and go from the house as it pleases. If there is room, two doors are ideal: one leading into an enclosed porch or utility area and another with a lock leading into the house itself. A locked flap should stop unwanted 'gifts' such as mice and birds being brought into the house while you are out. It will also prevent unwanted visits from the more adventurous neighborhood cats.