Next spring, get some compost and a pitchfork, and till the compost into the soil. I've had good results with Miracle Gro Garden Soil, which is available at any home and garden store, like Home Depot.
It will add organic matter to the soil, and break it up some, making it breathe and drain better. You can put some mulch on top of that to keep moisture in, if you choose.
Oh, I actually use the same soil for re-potting my indoor basil plant. Miracle Gro makes a potting soil, too, but the Garden Soil has worked for me.
CD