Do a Soil Test
The best time of year to add sulfur to lower the pH or lime to raise the pH is in the fall because these materials take time to alter the soil chemistry. Take some soil samples now and bring them to a lab for testing (many universities offer this service or you can send it to a private lab), or test it yourself with a soil testing kit. One of the best do-it-yourself kits is made by LaMotte. It will give you an analysis of nitrogen, phosphorous, potassium, pH, and more.
Create a Snow Trap
New England gardeners know that snow cover provides a benefit to many of our plants by protecting against alternate freezing and thawing of the soil. It also helps keep the soil temperature from dipping as low as it would without any snow. While we are largely at the mercy of Mother Nature in regard to the amount of snowfall, we can help our gardens collect the snow we're given. When cutting back perennials in the fall, leave about 6 inches of stalks. And when cutting the lawn for the last time, cut it high so the grass will help trap the snow.
Fertilize the Lawn
Grass roots continue to grow even after the plants go dormant, so fertilize the lawn one last time in late October to encourage root growth and get it off to a good start in spring. Use a nitrogen fertilizer and apply 1 to 1-1/2 pounds per 1,000 square feet.
Bury Plants With Mildew
Don't inadvertently spread powdery mildew by composting plants or leaving them in the garden. Cut down the plants, dig a hole, and bury them.
As you rake fall leaves, send them to the compost pile or spread them over annual beds. They will decompose faster if you till them in or mow over them with a lawn mower. They will protect the soil better if left on top of the beds. Either way, your garden benefits. If you use them to mulch perennials and shrubs, mow them into smaller pieces so they don't mat and contribute to crown rot.