Start looking for gardening catalogues, and start a gardening journal in a notebook, a calendar or purchase a gardening journal.
Check old seeds for viability. While doing that, paste a label on the envelope indicating when they should be planted, and whether they first need soaking. Sort them according to that timetable.
Indoor plants get dry at this time of year. Mist them regularly. Plants should be watered sparingly during the winter. Standing them in a tray of wet gravel is a good practice.
Rotate indoor plants every week or so to keep growth even.
Check indoor plants for insects and bathe with soapy water if you find any.
Remove heavy snow from evergreens.
Stomp a circle around the trunks of fruit trees that might be vulnerable to rodent damage.
Put the Christmas tree outside as shelter for the birds. Also smear the branches with peanut butter mixed with corn meal. The birds love that. Another use is to cut off boughs to lay on top of flower beds as added protection.
Keep bird feeders full.