Some veg require a long length of time between sowing and harvesting. Tomatoes, Chilies, Aubergines, and Cucumbers all fall into this category and will greatly benefit from an early sowing indoors. Since you will have all of your seed sowing gear out, you may as well get a good start on some herbs (Basil, Coriander, Chives etc), Lettuces, and maybe the odd Cauliflower or two. Leave plants like Sweetcorn, Squash, most Beans and Courgettes for April as they will just get too big before it is safe to put them outside.
I like to sow seeds directly into little degradable pots. If you are as non-delicate at handling things as I am, then you will find these very useful. When your plants are ready for something a bit bigger, you can just plant, pot and all, into their new home.
After you have some suitable pots, you need some seed friendly compost. Use multi-purpose compost at your peril! Most of the time it is far to rich for seeds and your failure rate will be high. Seeds are really only interested in light, warmth and a nice sandy or free draining soil. I use John Innes number 1 for seeds and it seems to do the trick just fine.
I then try to maximize my window space by getting a tray with a lid that will fit the most number of my little pots. The lid ensures that the original moisture from the soil will not evaporate. It also helps maintain a non drafty, steady temperature.
Then it is just an easy task of making a small indentation into the soil with a pencil or something suitable and dropping in a couple of seeds.
I do like to take a spray bottle of water to get the pots and soil nice and damp. I then drop 2 seeds in each pot and that seems to guarantee that at least one of them germinates. You must then be brutal and get rid of the weaker plant if they both germinate. A good tip here is to actually cut off the weaker one at soil level. That way you do not damage the good plant's roots by pulling up the one that is not needed. It is a good idea to get your labels marked up before you cover up your seeds. Make sure you don't use something that will disappear in damp conditions or you will end up like I did one year with a tray of plants with blank labels!
Pop the lid on and come back in a few days to be pleasantly surprised at your new indoor veg garden! If you don't see anything after 7-10 days, I would start to check the fine print on the seed packets (Expiry Date, Ideal Temperature, Time to Germination etc) but still show a bit of patience. At this early stage, it does not seem to be too important if it is a sunny windowsill. However, once the plants get established they will be hungry for more light.
Once the little plants emerge and develop their first couple of leaves (called seed leaves), then you can take the lid off. It is then vital to keep the soil slightly moist but, never let it dry out. I then usually just tip the remains of my nightly cup of water (how Eco-friendly of me!) into the seed tray and the pots absorb the water from the bottom.
Now is also a great time to start putting together your outdoor coldframe in order to house all of these plants round about April or early May. But I will leave that until next time.
**Update**
I am going to move the cucumbers to an April sowing. They are already 2 or 3 inches high and I can imagine them taking over my house by time they can actually go outside!