Planting sexed females

If I was trying to plant sexed females, how would this be done? I read on another site that you can tell the difference of male and females when there about 4-6 in. high. what stage of development would the plant have to be in? Any help or pics would be appreciated. thanks

You need to switch the light cycle of a plant from 18+ hours of light (vegetative stage) to 12 hours of light and 12 hours of uninterupted darkness (flowering stage) before it will show its sex.

Below is a picture of a male plant.


You want to make sure the plant has at least 4-6 nodes before you switch the light cycle to 12/12.

cheers