I’ve put down St. Augustine grass numerous times and it never did well until this year. I’d water it regularly all summer and yet most of it would die.
When I ordered a pallet of grass a few weeks ago, the farmer who grew the grass delivered it. He told me the trick was to water it heavily every day for one week, then water whenever you’d water the rest of your grass. For the first week, you want to water it so much that when you step on it you see muddy water bubble up. This breaks down the sticky clay soil that the grass comes in so that it will put roots down into the soil beneath. So far it looks like his advice worked.