Light Probably the most important requirement of growing high-quality transplants is adequate light. A full sun situation is preferable and this may be available through a south window, a cold or hot frame, or even a small greenhouse. Good light will help produce short, sturdy, well-developed plants that will transplant easily and withstand the transition from a protected environment to the elements of wind, temperature fluctuation and full sun exposure. The next requirement of good germination is providing the proper soil temperatures for the different species of plants. Soil temperature for the germination of broccoli can be much lower than that for peppers.
Moisture Be sure that adequate moisture is added at seeding time and maintained until transplanting.
Seedling flats or containers can be sealed in clear poly bags until germination is complete. This will guarantee adequate moisture since it recycles itself much like a terrarium. Only light applications of liquid fertilizer are required until transplanting. Most liquid or dissolvable plant foods should provide adequate fertility. Transplanting Timing is critical in this process.