Remove dead and dying stems and foliage from perennials. Be sure to to leave a few to protect the roots over winter.
- Plant hardy perennials and hardy evergreen shrubs in early fall.
- Plant deciduous shrubs and trees late in season when leaves have fallen.
- Remove and compost summer annuals.
- Plant spring-flowering biennials and bulbs.
- Transplant deciduous shrubs in late fall.
- Lift and divide hardy perennials.
- Lift and store, or insulate, tender perennials and shrubs before first frost.
- Lift and store dahlias and cannas after the first frosts.
- Take hardwood cuttings of deciduous shrubs.
This list was found in Learn to Garden: A Practical Introduction to Gardening. I did modify the list a little.