There is often little that can be done in the garden at the moment, except the eternal tidying up.
But you can get some seeds going in the greenhouse or on a windowsill. I can hear people saying: 'It's too late to start things from seed now!' This is true if you read the seed packets, but I have found over the years that late sowings often get the best results.
The early sown seedlings often struggle with setbacks and losses and they never reach their reach their true potential. However the late sown plant zooms ahead. There are less slight chills from draughts and very cold nights, the natural day length and light is better. If you are very lucky a well cared for early sowing can be well ahead come spring but often a late sowing overtakes it. I remember one year planting out a greenhouse full of tomato plants that were perfect and really strong, no setbacks at all. The very night after I planted them out there was a really hard late frost. Just as well that I had sown some late ones as an insurance.
So all you need is a few packs of seed, some compost, a pot or seed tray and somewhere to put them. A warm windowsill or even a propagator. There are no rules, the seeds know what to do, all they need is to be damp and warm. They should be sown thinly enough that they have room to grow a bit. Once germinated they will need light, otherwise they will go looking for it with long thin stalks that always cause trouble. What you want is a sturdy little plant ready to transplant into a pot or the garden. Then it will produce lots of flowers and maybe fruit.
This is where you take the credit; 'I grew those from seed you know.' But we will both know that the little seed did it all by itself.