What is the best method of growing grass in clay soil?

What is the climate zone where you are located and what kind of grass is it that you would like to grow? Knowing that may make a difference as to the kinds of answers that you will receive here. Just from my perspective, the best remedy for improving clay soil is to add gypsum which breaks up the structure a little and allows better drainage. Clay soil is rich in nutrients, however if it is not properly aerated and/or over-watered, problems can occur with poor drainage and air starved grass roots. Hopefully, others will come along with insightful advice of their own.

You will probably need to start with an excessive amount of lime. Then some fertilizer.