Rake out the moss vigorously
Improve soil drainage
Aerate compacted soil
Reduce shade by trimming trees and shrubs
Test soil pH
Apply lime if the soil is too acidic
Fertilize the lawn appropriately
Overseed thin or bare areas
Water deeply but less often
Mow grass at the proper height
Remove thatch buildup
Use a moss killer if needed
Repair low spots where water collects
Keep the lawn healthy and dense