Measure the diameter of the sprinkler head. Travel to the garden supply store and purchase protective sprinkler guards or donuts sized to your sprinkler. Choose a material based off what would look best in your lawn -- donuts come in rubber, plastic and concrete varieties.
Dig up the grass around your sprinklers, including the roots. Remove only what will be covered by the sprinkler guard.
Center basic sprinkler donuts around the sprinkler, settling the donut into the depression created by the grass removal. Slip the donut's hole over the tip of the sprinkler head. Install more advanced sprinkler guards according to the product instructions.