Reduce the amount of water you supply to your lawn. Moss loves soggy, constantly moist soil and grass conditions. Instead, only irrigate your lawn when it starts to display signs of drought distress -- a slight folding of the grass blades is one sign -- and try not to water in the evening.
Prune back overhanging tree branches, thick shrubs and tall hedges. Moss does best in shade, and a moss invasion in your lawn typically means your yard isn't getting enough sunlight. Increasing sun exposure dries out the soil, discourages moss growth and also helps encourage the grass to grow thicker, which in turn makes it less susceptible to weeds and moss.
Rake your yard vigorously with a metal-tine rake. This peels back and breaks up the mats of moss. Collect the uprooted moss and lay it out in the sun to dry and kill the growths.
Spray your raked lawn with a moss-killing lawn spray formulated with either potassium salts of fatty acids or iron sulfate. Mist the affected area evenly according to the specific spray manufacturer's guidelines. This "burns" the moss and kills it completely without causing excessive harm to your existing grass.