You have to check around the 4th node. If you see any sign of little balls at the node, its male, if you see hairs its female. It's really a lot more complicated than that but I don't quite know how to explain it. Someone will help, its still probably early to tell anyway.
veg untill 8"tall(4/8 weeks).
you can only tell the sex once into flowering mode.
depending on strain about 2 weeks in to flowering you can sex them easy and pull the males.
were the shoot off the main stem starts u will see 2 small leaves more of a pre leaf if thier rounded good chance r male if pointy good chance fem hard 2 sex at that stage
Don't add that 3 hour space on purpose, the 18 on 6 off, is good for the plants. The idea is to mimic outdoor light though right? It's not really realistic for there to be a weird 3 hour period every other day. The light will be on and stay on, until night (your off period).
dont screw with lighting times unless you want problems... stick with what you have till you are ready to flower, then change to 12/12 and stay away from them the lights are on...
18 on 6 off until your plant is at least 20 inches tall is the best bet.... way to early to tell sex yet.... I vegged for over 2 months before mine started pre sexing (showing signs of sex ).....good luck...
some people dont have enough room to wait until they are 20 inches,
remember they almost triple in height in flowering so that would be around 5 feet,
thats massive for an indoor plant unless you got the room