I usually start the seeds, put them in 1qt gladware with dirt once germinated, leave them under 24 until they r big enough for 1 clone, take that clone, root it, right into flower as soon as she roots, within a week after that you know what the sex is. that way there is only a small amount of dirt lost if male and if it's female you don't have to wait for the mom to switch back into veg and grow all those crazy single bladed leafs and what not just shove her in a bigger container and more clones are ready within weeks. takes a little longer to find sex initially, but in the long run it actually saves a little effort and time.