Grass can die for a number of reasons. Cold winter weather, dog urine, disease and insects are some common problems leading to dead grass. A few solutions are available.
For most grass types, raking away excessive levels of dead grass in dead spots less than 2 feet will allow the grass to grow back. For insect or disease control, you may need to add herbicide or other corrective solutions to kill intruders.
Planting sod in dead spots will provide an instant correction for dead spots. You can plant seed in the dead spot after clearing and preparing the soil but growth will take much longer than sod.
Find out how or why dead spots occur in your lawn prior to correcting them. This preventive maintenance allows you to find permanent solutions if you are constantly repairing dead spots.