this is the best site i've seen to help with this question

[url=http://www.weedfarmer.com/g2.2/main.php/male-female/[/url]

female - can appear to have little balls but the key is that females will have delicate white-ish looking pistils that come out

male - balls, little pods, no hairs.....chop down throw away

only females produce buds that you want to smoke. is there a little thc in males...yea...worth it? NO! chop down throw them away before they pollinate your females.

how early is a matter of genetics, environmental factors, etc. trust me as your plants get older, you can't miss the development of sex. just look closesly