As they shortest day approaches there are still many green fingered things you can still do, if you feel like braving the cold.
Now is a good time to plant bare root roses, deciduous shrubs and ornamental trees whilst they are in dormancy. If you feel your garden needs more winter interest you could consider adding shrubs or trees with ornamental bark. Cornus sanguinea "Midwinter Fire" with its vibrant orange/yellow stems will definitely brighten any border even in the gloomiest of winter months.
December is a month in which you can train fruit trees growing against a wall but don't prune them. Do prune Acers and Vines before Christmas. The beautiful bark of Acers can be used to make some interesting last minute decorations.
If you haven't yet, it is good to prepare the garden for some colder weather ahead. In cooler regions more tender plants will need to be covered in fleece to protect them over winter. If you have tree ferns you can put straw in their crown to help them through the cold.
Put pots near the house in a sheltered spot and or wrap them in bubble wrap. If you have any empty ones then why not plant some winter bedding alongside evergreen perennials with interesting foliage like Heuchera.
If you like the idea of a live christmas tree this year there are many people who offer a tree rental service. I know some companies will keep the same tree for you year on year. Lovely idea!