When sowing seed it's important to use the right sort of compost. Seed compost is low in nutrients. Specific seed compost is available although coir compost is also ideal, alternatively use sterilised* soil or a multi-purpose compost mixed with vermiculite or horticultural sand.
Gently water the top of the compost with a spray bottle or watering can fitted with a fine rose. Use tap water rather than water from a butt as this can introduce infection. Doing this first avoids disturbing the seed, once you have sown them.
Sow seed sparingly to make it easier to prick out later.
Cover the seed lightly with compost, as a rough rule of thumb seeds should be planted 1½ times deep as they are in size. So the larger the seed the deeper it needs to be planted.
Cover the seed tray with a piece of glass and a sheet of newpaper until the seeds have germinated.
Write the seed variety and date sown on a plant tag and stick it in the side of the tray or pot.
* sterilising soil prior to use will reduce the chance of soil borne diseases affecting the seedlings.
Pricking out - transplanting and potting on
4-6 weeks after sowing, the seedlings should have produced their second set of leaves. Which means that they are large enough to pot on, hold onto one of the lower leaves and gently lever the roots up, trying not to damage them as you lift.
Using a finger or dibber make a small hole in a pot of potting compost, still holding the leaf, work the roots into the hole, gently firming the soil around the stem of the seedling. The plant should be at the same depth as when it was in the seed tray.
After potting on, don't forget to water with a fine rose. Use tap water rather than water from a waterbutt, to avoid introducing bacteria that may cause 'damping off'.