How much time you spend with your cat will depend on your pet's needs and personality. A good rule of thumb is to schedule at least two to three play sessions - 10 to 15 minutes each - per day, but it's best to let your cat dictate the specific time frame as some may want to play longer and more often, like kittens, and others may want shorter play time, like an adult cat.
Which part of the day you spend playing with your cat is almost as important as how often you play. Morning is a great time to play, as your cat has waited (patiently, we hope!) for you to wake up after the long night, and she'll be delighted to get your attention. Late evening, right before bedtime, is another excellent choice. Since cats are nocturnal, giving her a chance to expend energy right before you go to sleep may help her - and you - have a quiet night. Playing before mealtimes is also a good choice, as the meal will serve as a reward for her good behavior. Play before eating also stimulates her appetite.
The best time of all to play with your cat is when she wants to play. She may be too sleepy in the morning to play, but ready and willing for a late afternoon romp when you return home from work. Whenever practical, let her set the schedule. She'll love you for it.