Instructions
Make sure the cat doesn't get outside, where male cats will be waiting to impregnate her. She will try extremely hard to escape and find a mate, so be vigilant.
Exercise your cat by giving her new toys to play with, tossing a ball, or using a laser pointer. In this manner you will work off some of her excess energy and distract her yearning for a mate.
Visit the veterinarian and discuss giving the cat hormone injections, similar to birth control but given to the cat only when the heat cycle has begun. This solution is temporary, as well as costly, since a female cat will come in heat several times a year.
Clean the litter box several times a day; a cat in heat urinates more often.
Put diapers on the cat during her heat cycle. This are available at pet stores and will prevent spraying and mating.
How to Care for a Female Cat in Heat
Female cats that are not spayed to go into heat, or estrus, every few months. During this time the cat will become more affectionate than normal, rub herself on the carpet, spray urine, and meow loudly to attract a male cat. Caring for her during her heat cycle consists of keeping her from getting pregnant. The only way to prevent your cat from going into heat is to have her spayed.