yes you have to get rid of the males so they don't pollinatr the females and the best way to tell the sex is about a week or so into flowering (the lights on 12/12) you will start to notice 2 little white hairs coming from the base of each internode the males have little balls instead hope it helps try investing in a good grow book let us know more about your setup
if u do a search on it, u will find great pics of male and females... males will show sex first then females.. at least take 2 weeks to sho preflowers....
ill tell u what i did. i putt them ina cup in wet papertowel and let them sprout then planted them and watered them every day and i turn the light on alittel bet
yeah, you can't tell till they get bigger, and you have the light schedule on 12/12, then about 7-10 days later, you'll be able to tell..........Peace out........Sid