If your cat's already been through a heat, you won't forget her howling and the constant demands for attention. If your cat isn't able to mate, then her heat is going to be a frustrating and uncomfortable time for you both. If your cat is able to mate, then you need to be prepared for potentially two litters of kittens a year! Unless you're planning on breeding, the best cat care would be getting her spayed. It will be easier on her and it will be easier on you.
When your cat is 'in heat' she is in the fertile period of her reproductive cycle and is looking to mate. A cat will usually go into heat in the spring and autumn and a heat can last from a few days all the way up to a few weeks. A cat usually has her first heat at around 6 months of age, but some can have it as early as 4 months old.
During a heat your cat may be more affectionate, rubbing up against furniture, walls and her favorite people. She'll probably rub with her hindquarters in particular and may frequently display the mating position with her hindquarters and tail raised. The most problematic parts of a heat for an owner are the vocalization and spraying. Cats in heat will howl loudly and constantly as they try to attract a male to mate. They may also spray walls or furniture with strong-smelling urine also in an attempt to indicate their availability to a male. If you have an indoor cat, they may try desperately to get outside, even going as far as attacking windows or doors.
Although your veterinarian may be able to prescribe medication to reduce the signs, the best way to prevent a cat being in heat is to have her spayed. After she's been spayed, she will stop going into heat and will become much less territorial and less likely to spray or scratch.