After having a professional soil test done, I've become obsessed with this, and over the past few months, I have had a lot of discussions with University soil scientists, people here, other forums, etc. I think the single best thing you can do is mulch mow. It's free organic fertilizer. The microbes will come naturally, you do not have to spend the money on compost to inocculate, microbes will build naturally. Compost is great, but mulching will do it if you're like me and don't want to spend the money on commercial compost. From my discussion with University scientists, if your soil is low on something, like mine is low on P, there is nothing wrong with synthetic fertilizers. Organic matter is important and that's where mulching comes in. It's going to take 3 or 4 years of nothing but starter fertilizer to get my phosphorus right. It would never get there if I was pure organic. When my numbers are right, I may just put down some Nitrogen in the early fall and rely on grass clippings rest of time, but until then, a balance of synthetic and organic (mulching) for me. I calculated my clippings, after evaporation of water from blade, I am adding about 4 lbs of organic matter per 1,000 sq ft every time I mow. That's a crapload of free mulch per year to feed worms and microbes.