One of the most rewarding things to do in the garden is to sow your own seeds, from the prized flowers and vegetables you saved from the previous year. I always feel like such a smartarse when they come up too. It intensifies everything else you do with that plant from moving it into a pot, putting it in the ground and the entire husbandry involved in maturing it to its full potential.
Receiving new seeds in the mail or going seed shopping is also exciting, but best is being given seeds. If I'm not sure of the name of the plant I just name it after the person who gave it to me, which means when I go for a walk around the garden I'm always among friends.
The actual business of striking seeds can be a fickle affair. If I had to identify the two biggest problems I've had with my seed raising it's been too much moisture and not enough moisture. I've also fried mine in the sun, had them blasted out of the tray by rain, eaten by snails and nailed by Jack Frost. But all of that has finally been remedied, because the one thing all these problems have in common, besides sounding like the seven plagues in the book of Exodus, is that they are all the result of human error and that is what I have just reduced. A few weeks back I constructed a bamboo and clear tarp green house, installed a bit of irrigation on a timer and all of a sudden it is not too hot, cold, wet or dry, the snails are under control and Mr Frost is not going to be a problem.
All I have to do is check up every day or so on progress and make sure that it is all running smoothly.
As well as reducing my own inattention variables, the medium you plant into is also important.
In most cases a good medium is described as inert which means it has no nutrient. In fact I've had some of my best success in pumice sand which is defiantly inert but it's also good at retaining heat and absorbs a bit of water so isn't as dry as you might imagine. Seeds have everything they need on board so it isn't until the plant starts photosynthesising that it actually needs feeding. A good all round commercial seed raising mix is Black Magic which we use a lot.
Most seed packets have a guide to how deep you need to plant, but if you are in doubt it is best to plant a bit on the shallow side. I've had more problems with seeds being planted too deeply than too shallow. More often than not shallow seeds seem to point themselves the right way up and get their root into the seed mix.
There are many ways to sow seed and which one you choose depends largely on what you're sowing. You can broadcast sow or sprinkle or throw the seed into trays. If the seed is really fine you can mix it with a little sand to spread it around. If you don't do this, so many minute plants may come up that the whole tray becomes unmanageable. The sand spreads the seed around a bit, giving each seed more space.
Many plants like carrots need to be direct sown into the garden. My best success here is sowing the seed into a mixture of finely crumbled dried cow poo and sand mixed into the surface of the soil. Carrots are broadcast-sown so the same trick of mixing the seed with sand can work well here too. Once the carrots come up they need to be thinned out and covered with a layer of shade cloth, kept off the ground with sticks like a rough tent, to give the young plants good protection from too much sun and moisture loss.