If you're starting a lawn from scratch, April is the month to lay down sod, when it's cooler and there's time for the grass to take root. Ask your seller for grass that suits your yard's conditions, whether sun, shade, or a combo. Sod should be fresh when you lay it; beware the rolls that have been sitting outside for a while. Prepare to water, water, water when it's installed. Your garden center can recommend an appropriate schedule.