The first thing you need to realize is that you can't physically jump in and hit the cats, or move them apart using your hands. This could result in the cats attacking you, or with you aggravating the cats even further. Always avoid using your hands when trying to break up a cat fight.
One option that you have is to use water; you can either use a hose, or a spray bottle, and splash some water on the cats. This normally ends up making the cats break up the fight and makes them move apart. However, if your initial attempts don’t work out, try directing the water towards their noses, as these are fairly sensitive.
If you want to separate two fighting cats, you can always use a big broom to separate them. Just stand at a safe distance, and slowly move the broom between the two cats; then, push one of the two away from the other. This will distract the cats and break up the fight.
Cats are normally very scared of loud noises, so if you can get your hand on an air horn, or something along those lines, then you can use it in front of the cats. This will startle the cats and make them run away in opposite directions.
The last option that you have is to use food to lure the cats away. No matter what the cats are doing, if you offer them fresh pieces of chicken or fish, the smell will make them forget the fight and follow you, asking for the food. The best option is to keep some of this food handy if you have more than one cat. However, don’t always use this method, as this will result in the cats fighting just to get food.