Here's a terrific short article on soil life and how to care for it courtesy of the Nebraska Statewide Arboretum. My personal strategies for success growing a native wildlife garden extend from the piece, so here is my list for a relatively care free perennial garden:
1) Top dress, do not till in, a layer of compost. Some suggest 1/4 to 1/2 inch, but I say go bold and do 1-2" if it's a new bed. Lincoln's LinGro compost is free and very rich -- you can smell how good it is.
2) Mulch with organic material, like wood chips (also free from the city), 1-3" thick based on soil type -- for damp clay, 1" of mulch might be best. As the garden grows you can mulch with its waste, for example using the spring cut down as mulch. Those old stems from last year break down and feed the soil very well, and the hollow-stemmed cuttings provide shelter for insects and spiders. NEVER ever use rock as mulch -- it dries out the soil acting like a heat absorbing radiator, and leaves openings for weed growth (and it adds no nutrients to encourage soil life).
3) Plant thickly and plant with height and foliage shape variety. By doing so, you shade the soil, which inhibits weeds and helps keep moisture in the soil (as mulch does). Plus it looks better and brings in more wildlife.
4) Right plant for your soil, moisture, and light conditions. Choosing a plant native to your locale is a good first step, but then you need to make sure it likes it dry or wet or sunny or shady or clay or sandy. Don't trust vague plant tags. Google the latin name and take a poll from several sites.
Improving soil health means improving plant health and resiliency. It also means a near total elimination of fertilizer and pesticides. It means a carefree garden -- and it works. Trust me. It will take a few years to get the soil alive and dynamic again, especially if you're in a new housing development, but it will work.