New growers often ask 'how can I tell if it's a boy'?
It's not difficult really once you know what to look for and when.
For regular photo-period plants they usually show from the 4th/5th week of life and are usually located on the 3-5th branching node. This happens from the 3rd week of life when growing regular auto-flowering plants. Males usually show their sex before females. If you look carefully at the branching points you will see those little, stripey sacks on a little stalk developing which confirms you've got a Boy that's sexually maturing and about ready to start producing pollen.
The easiest way to demonstrate this is simply with a pic that show what the first little pollen sacks look like. The top arrow shows an early male preflower, the lower arrow shows pollen sacks just a few days more advanced.
Shimples 
(Note to self : Get another, slightly earlier male-preflower picture)
