re: Improving Drainage and Leveling Lawns with Heavy Clay Soil

Deal with drainage 1st. Have the yard elevation surveyed and redirect water with broad, shallow swales. Next start converting the clay to a topsoil by tilling in whatever composted organic matter is cheap in your area. I like cotton burr (after-harvest/ginning husks and stems). Plant a winter cover like crimson clover and till that in early spring. You might do the yard sector by sector, but it will be a multi-year project.