telling the difference

my name is richard,i currently reside in norcal..in Novato just north of San Francisco..i am a medical marijauna patient...i recently planted 6 small plants that were from seeds not clones to the best of my knowledge...my question is how can i tell the difference between the male and female plants..i have other medical marijauna growers in close proxcimityto me,so i want to avoid pollunation of there outdoor crop...the plants right now are between 3-5 " tall..and does anyone have a suggestion on literature to read on outdoor growing for novices...:smokin: