Timing is critical. If you start your seeds too soon, they may grow out of their containers before spring arrives. Start them too late and they won't be ready in time. A good rule to follow is to start your seeds about eight weeks before the last expected spring frost. Consult your local weather channel or conduct an Internet search for the almanac forecast in your area.
Choose a starter planter with proper drainage. Get creative! Seed flats, peat pots, plastic cups, egg cartons, even takeout boxes with holes poked in the bottom work well. In general, your planting containers should be at least 3" to 4" deep. Fill them to about 1/4" from the top with soil.
Egg cartons and peat pots need to be soaked in water before adding soil and seeds or they will draw moisture out of the soil.