4 parts compost
1 part perlite
1 part vermiculite
2 parts peat moss
That there is little to no nutrition in the mix, because seeds come with their own, built-in nutrition.  (“A seed is a baby plant in a box, with it’s lunch.”)
Seed starting mix is finer than other  mixes, so it’s important that the compost used is very fine. ~Sherri Morgan, Master Gardener & AGC Board Member