You normlly don't see definate signs of male or female until flowering starts. Taking a cutting and putting it under 12/12 will tell you the sex of the parent. Some strains will show pistils during vegetative growth. This is an indication that it is a female plant and seems to be getting more common as the undesirable traits get mixed into the current gene pool. A LOT of purple strains seem to show pistils during flowering and it seems more common with clones. Years ago, before the current mixing of the genes became crazy, pistils during flowering was usually a good reason for killing off the plant, since it can be more prone to herming sometimes. Times and plants have changed, so look for the pistils... if you see them, it's a female. You can generally get male flowers on a female plant also, but I don't think I have seen female pistils on male plants.