One of my favorite fall projects is to enlarge a garden bed, update a weedy path or update a weedy garden using Lasagna Gardening techniques. As in the picture, this involves using several layers of paper, leaves, compost, mulch etc. to build up the soil.
Collect enough large, heavy cardboard boxes and newsprint to cover the area. If you are updating a garden, remove the plants you want to keep, removing any weeds hiding in the root balls. If there is vegetation, mow or weed whack the area to level the space. Next, add a layer of overlapping cardboard with landscape staples or stones to keep it in place. If there are woody plants, wrap the bases with brown paper or newsprint. For a path, just mulch over the top, but for a new bed, rake leaves onto the area and cover with compost and mulch. Wet the area down to settle the materials and keep everything in place. In Spring, you are ready for your next garden adventure.