Planting grass seed in March, depending on the climate where you live, can be considered spring planting or winter planting. In mild climates, where you have sun year round, planting grass seed in March will be a fairly easy job. Warm season grasses will do well as long as the temperatures are nice. In snowy cold climates, you can still plant grass seed so that it might sprout in March, but this will take more advanced planning and preparation to make sure the seeds will be ready during the spring snow thaw.
Whatever type of climate you live in, it is important to prepare the soil prior to planting the seed. Till the soil by turning it over with a Rota-tiller or shovel and rake. Remove weeds, rocks, dead grass and sticks. Add some good top soil if the soil nutrient is low. Level the ground and smooth out the soil so water won't collect in puddles. Preparing the soil in a cold-snowy climate needs to be done before the ground freezes, in late summer or early fall. In a mild climate, you can do this soil preparation in the month of March.
Choose which type of plant seed you will plant. For mild sunny climates, almost any type of seed will do well. Look in your garden store for grass seed that is tailored to your climate. For cold climates you need to choose a seed that can lay dormant under the snow until March. Look for seeds that are still in their hulls such as, unhulled rye grass, fescue or Kentucky bluegrass. Unhulled seeds will be protected by their 'shell' until the snow melts.
Another method for snowy climates is to lay the seed on top of the snow in the month of March and when the snow melts the seed may sink into the earth and sprout. You can lose seed with this method, especially if it is windy or the runoff is strong, taking the seed to another location.
Plant your grass seed 1/8 to 1/4 inch in depth before the first freeze or during the month of March. The seeds need to have good contact with the soil to germinate well. Use a seed spreader to spread the seeds for an even result. Follow the directions on the bag of seed. Rake the seeds through the soil so they will be surrounded with soil.
Fertilize the soil with a good starter fertilizer. Use a spreader for even coverage.
Water the grass seed. Keep the ground moist by sprinkling it in the morning and afternoon. Seed planted underneath or on top of the snow will be watered by the snowmelt so you do not need to water the unhulled seed until the snow is completely melted.