Moss can be a real problem and even tougher to control. Start by raking out the existing moss. Moss usually grows in damp areas with poor air circulation. So control entails first improving drainage (or removing cause of excessive moisture) and improving air circulation, if possible. Prune up low hanging branches and move fences or other obstructions to air movement. Anything to get more sunlight and air will help. Also, use Core Aeration process to break up the soil. Moss will not do well in loose soils. Finally, test the soil and add sulfur to lower the pH if you can. Moss will not grow on a healthy dense turf. Be sure you are following good watering, mowing, and fertility practices to encourage a healthy lawn.
Some people have reported that by using the dish soap "Dawn Ultra" at a rate of 5.0 ounces per gallon of water, that they have seen moss problems disappear. While we cannot back this up with research results or even personal experience, it might be worth a try. Also, whether or not other brands would work as well is unclear. Let us know if this method works for you - or if it doesn't!