Our female came into Florida last winter to FLchams, where she laid about 80 eggs. Mike of FLchams then shipped her to us, after her quick recovery. So, there was no mistaking that. In fact, knowing we already had a confirmed male, Kristina of MelleriDiscovery contacted us when Mike of FLchams got his shipment in. She said there were gravid females laying eggs and that it would be a good opportunity for us to get a confirmed female. We are so glad we did.
Our male was purchased from a local Mom & Pop pet shop. Once we owned him and got him acclimated, we caught him humping the furnishing in his cage. He also would pass fresh goo from his vent. We got a sample and viewed it under a microscope and confirmed the presence of live sperm. We have a video of that microscope slide. So, again, we were able to confirm gender.
Once we got our female, our male stopped humping the furniture in his cage. We built the free range for them and they lived together for a year before deciding to take the plunge.
I'm not sure how others discover the gender of theirs, except perhaps by trial and error.
I will post photos of the free range later.