Fall is a great time to start updating your landscaping and a great time to plant shrubs and small trees. The cooler weather allows the plants to get established.
Usually, you don't need to amend the soil, aside from laying down mulch. You want the plants to get used to their native environment. Mulch will help keep down the weeds and keep in moisture.
For more information, visit aggiehorticultuture.tamu.edu.