Most seed packets tell you when to place transplants in the garden relative to your last spring frost date, and how many weeks prior to transplant to sow your seeds. Add up the weeks, and count backwards from your frost date to determine the sowing date. For ease, group your seed packets together by date. When the time comes to sow the seeds, gather your plant labels, pots and trays, grow lights, and bags of seed-starting medium. Make sure you have a warm spot to place your planted trays, because most seeds require warmer temperatures for germination than for growth.
Some seed packets list the optimum temperature range for each plant.
Next, pour some planting medium in a dishpan or bowl and mix it thoroughly with warm water. Allow the soil to sit for a while to absorb the water before filling your pots. Use this time to make plant labels for your seedlings. Using a waterproof pen, indicate the plant name, variety, and planting date on the label. Again, refer to the seed packets to see how deeply to plant each type of seed, and use a pencil to make planting holes in the medium.