Flea control products containing pyrethrin can be effective at killing fleas on a lawn. Cedar mulch doesn't kill fleas, but it does repel them along with other nuisance insects.
Fleas are attracted to dark places, so pruning trees and using plants that allow light through can reduce the amount of fleas in a yard. Wildlife and domestic animals often brings fleas into a lawn, particularly if they spend an extended amount of time there, so setting up a fence can help. Fleas also tend to stick around in tall grass; determining the proper height for a lawn's grass variety and cutting it regularly can lead to fewer fleas.