To get these conditions, you first need to remove any vestiges of the old lawn. Renting a sod cutter for about $75 to $100 a day allows you to slice off old grass and weeds at the roots. Then it's time to turn the soil with a rotary tiller, adding sand and compost in successive layers to achieve an ideal mix.
But even with these additions, no soil is ready for seeds if it doesn't have the right pH. The pH scale measures acidity and alkalinity, denoted by numbers from 0 to 14, with 7.0 being neutral. Grass grows best in soil that has a pH between 6.0 and 7.5. If your soil is too acidic (below 6.0) — a common problem in cooler wet climates like the Northwest and Northeast — you can add lime to bring it up. If it's mildly alkaline (7.5 to 8.0), a little peat moss, which is naturally acidic, should correct it. Soil that is very alkaline (more than 8.0), which is more likely to exist in dry, hot climates, needs sulfur.
All soil could use a little fertilizer boost to nourish the seeds. Then once the soil is ready, the actual planting is cake. Just throw out the right amount of seeds, gently rake them into the turned earth, and make sure they get enough water to keep on growing.