Mark high and low spots with stakes or spray paint
Remove rocks, roots, and debris
Mow the grass short
Measure the slope with a string level or laser level
Cut down high spots with a shovel or sod cutter
Fill low spots with topsoil or leveling mix
Spread soil evenly with a rake
Water lightly to help soil settle
Compact the soil with a lawn roller or by walking over it
Recheck the level and add or remove soil as needed
Reseed or lay sod on bare areas
Water the yard regularly until established