you veg them, when you are ready to flower you start flowering and monitor the plants closely and be on the look out for any plants with male pollen sacs and remove the male plants from the grow room and kill them so you dont end up with seeds in yor buds. or you make a cuting (clone) from each plant that looks the best in your 12 seeds and identify your clones to know what plant it came from. when the clone are ready flower them and identify the males from female clones. And use the mother plants that you identified as females to make clones for your next grow!