When cat fights stop at growling and cuffing, rather than the drawing of blood, you can probably sort out the problem yourself. The next is to see your vet.
Begin a “cat fight” diary. For a few days record the details of any aggressive encounters, noting when each one started, which cat initiated the squabble and what happened. This record will come in handy when you try to restore peace.
Take both cats to the vet and arrange for neutering or spaying if this has not already been done. Aside from all the other problems, such as spraying and unwanted kittens, intact cats are much more likely to fight. If the cats are fixed and have been together for a while, and one has just started exhibiting aggressive behavior, take him to the vet. The sudden aggression could be the sign of an underlying medical problem.
Give both cats equal amounts of attention and petting. If you stroke one, get up and stroke the other as well. Do not make a show of petting one in front of the other to try and make a point, for example if the other was growling. This will only encourage jealousy.
Separate the cats at the times they are most prone to fighting. Often this is at feeding time, when cats feel defensive. In this case, feed the cats in separate rooms and keep them separated for about half an hour after meals. Provide at least one litter tray for each cat, if they are indoor cats. Sharing a litter tray can be stressful, especially if one wants to go while the other is in occupation.
Break up any actual fights by making a loud noise or, if necessary, squirting the cats with cold water. Keep them in separate rooms until they have calmed down.
Consult an animal behaviorist or your vet if the aggression continues. It may be possible to work through the problem, but if not, one of the cats might need to be re-homed. This is another time when the cat fight diary will come in useful, both to the animal behaviorist and when you're deciding whether one or both cats need to live in single-cat households.