Hey Hodot. It is so wonderful to hear that you are going into psychology. There are some magnificent books you should read, like Tomkin's series of Effect, Imagery and Consciousness. However, these are quite thick and require disciplined study, I've found. I suggest starting first with Malcolm Gladwell's "Blink" then going onto "Descartes' Error" by Antonio Damasio, and then "Mindware: Tools for Smart Thinking" and then, finally, Tomkin's E.I.C. These are often intertwined with neurology, however, but that should prove to be enriching rather than stumbling. I also suggest reading the two books "Ignorance" and "Failiure" by Firestein. Though these are not required, I've found them very helpful to approaching things differently.
Anyway, on the original subject, It's good that you're gaining experience in this area. Studying these things will serve as a useful tool in the future. The following words come from experience and my own study, though I haven't given too much thought to the more dubious parts of sociology.
Polygamy (related subject) has a very troubled history, as it usually results in wives competing with each other, or one gets more attention than the other, etc.
The reason I bring this up is because the same can happen to polyamory, though not as severe. Flirting with multiple people isn't a good idea, because that will most likely get publicized through the other person's gossip, which spreads like wildfire. Especially because these are young people that you're dealing with who most likely do not have a lid on their mouth (they try to convince you that they do, but really, use your common sense here.) Keep your image as clean as possible, and think about the effect your actions may have in the long-run. In addition, think also about the effects that other people's actions will have in response to what you do.
You can find out a great deal about people just by asking them direct questions. How much you sugarcoat the question depends on the person, so whey them up as best you can by observing their body language. Remember, there is a time to speak and a time to stay silent, so choose the best time to ask the question - and make sure you ask the right questions so that you get the information you want. This is more easily achieved when you are seen more as a friend rather than a date, as they will reveal more to you because the fear of "putting you off" will be reduced, if not eliminated to a degree. If you observe courtship post-1920 to pre-1950, you'll get the picture. Don't be afraid to tell them why you're there in the first place, people like to know what they're dealing with.
P.S. Think about how the other person may feel about this arrangement. The trans person you were talking to obviously wasn't too happy with it, he's just being polite.
I don't really know what else to suggest past this. Is there anything else?
