First question is what are you growing in the raised beds? If it is vegetables than make sure any grass clippings are free of weed and feed products. The leaves you add should be small or partially rotted or they may not break down by spring planting time. Leaves and grass clippings are organic matter and you can add one to two inches on top of your soil and dig this in a bit so the matter will partially rot before spring. It is often easier to just add compost on top of the soil in the fall and work this in once spring arrives. Compost can be bought in bags at a nursery or made at home. Keep growing, Marianne Binetti