Shade: Your lawn will grow in optimal conditions where it receives a minimum of four hours of direct sunlight per day (in the heavy traffic area, the minimum sunlight exposure increases to six hours of direct sunlight exposure per day).
For shady areas of your lawn that receive less than recommended daily direct sunlight exposure, you may consider a different type of grass species to accommodate better growth and tolerance. For example, the Creeping red fescue type of grass is more tolerant of shade than Kentucky bluegrass. Further adjustments to mowing, watering and fertilizer application will help partially remedy and make your lawn better adjust to shade and lack of exposure to the sunlight.
Mowing: Do not mow any shady areas of your lawn to less than 3 inches in height (versus 1.5 inches to generally recommended height of lawn in sunny areas of your lawn).
Fertilizer and Water: Fertilize and water shady areas of your lawn less than full sun-exposed areas. Overwatering the shady part of your lawn will cause the sitting moisture on the lawn which can contribute to disease, weed and pest growth and infestation and damage to your lawn.
Keep the traffic off the grass: If the shady and problematic area of your lawn is exposed to heavy foot traffic, you may consider installing stone, bark or another medium that is more tolerant to shade and the foot traffic.
Check shady and wet areas more often for disease and pest presence: Diseases such as powdery mildew are often found more in shady and wet areas of your lawn. Checking for any issues in shady and wet areas of your lawn such as corners, under or near trees etc. is recommended.