What’s the best way to plant grass?

I'm needing to put St Augustine in about half of my front yard. I know it's a great grass for H-town, but what do I do about the s**t weeds and clover that's there now? Do I shovel out the top 2" of dirt and weeds and just haul it to the dump? Do I turn the top soil and fertilize it before I put down the squares of grass from Home Depot?