You can cut back your perennials now, but hold on...don't cut back too far! A little bit of foliage left behind goes a long way in protecting against frost damage. You can leave dried flowers, ornamental grasses and seed heads that look good to provide food for the birds through the winter. Pull out annuals and clean up leaves and weeds in the bed.
Apply a fertilizer, such as Milorganite to give your lawn a great head start next Spring. Mow your lawn one last time before the winter sets in. Either rake your leaves off the lawn or if you don't have a lot of leaves you can mow over them several times to shred them and start the decaying process. If left on without being shredded they can suffocate your lawn.