Probably the biggest joy in gardening is planting. What could be more fun than planting again, or trans-planting?
Until Dr. Christiaan Barnard moved a human heart from one body to another in 1967, transplants almost always meant taking small plants or seedlings and setting them out into the fields and gardens.
If you want transplants, you have to start with seeds. The idea is to increase the growing season by getting seeds to sprout and grow some true leaves before planting. Also, by growing your own transplants, you have access to thousands of varieties of garden plants rather than just what's available at stores.
First you will need fresh seeds. If seeds have been stored properly you can hold them over year to year; whether they're purchased seeds, or seeds you save yourself. Seeds often rot in wet damp cold soil so even if you just get an inch or so of growth you may be weeks ahead of seeds directly panted in the garden.
Next you will need soil or a growing medium. You can use garden soil but you may be introducing a lot of pests and disease, with no natural predators. It's better to use a sterile growing medium or potting soil. The advantage of soil-less mixes is that you don't get soil borne disease or bugs.
The mix will only hold the seedlings in place and they will need additional fertilizer to grow. You can make your own soil-less seed starting mix, including the famous Cornell formula developed in Ithaca. Mix together four quarts of sphagnum moss, two teaspoons of ground limestone and four teaspoons of granular organic fertilizer.
Fill your pots or flats just to within a quarter-inch from the top with the potting mixture. Gently level the surface and water well, even before you plant anything. This will moisten the mix and settle any air pockets.