 deep and infrequently, and if you've mulch mowed, and if you've fertilized right, which is to say not too much and not too little, mowing high, that's one of the real keys on this one. Maybe one of the most important factors. If you've mowed high and you have all these other factors in place, then you're going to have a thick yellow lawn that is going to shade out the weed seeds that could sprout.