As you grow you will become familiar with how a plant grows. First you get fan leaves, and stipules, then nodes sprout out of the base of most fan leaves.
You won't be able to sex a plant accurately until you see the final stage of growth, the calyxs. These are the sexual anatomy and they sprout between the stipules and the nodes.
Even when these first show up they are very difficult to sex, but without them you have pretty much zero chance unless you're a plant whisperer.
Here is a pic from my own plant showing where. I have determined that this is a female, but i was not able to from the area shown. in my higher nodes i have pistils: