Well now, you've received a number of rather frowning responses, but it is of course possible to see if someone is gay or straight. I don't know of any spread: perhaps you can design your own if you want one? But apart from that I think the best thing is to get to know your cards intimately, not by set meanings, but by exploration and thinking and developing your sense of observation and intimacy with the cards. They are your cards, you ought to be able to know them like your own smell. You also practice reading for yourself and for as many people as you can - and remember this is their lives you're motivated by, not your curiosity. Practice your intuition. Eventually you will get to a point where you know yourself and your cards, and are so open to other people, that facts about them that you are meant to know you will see in your cards.
There is no quick fix to understand the infinite variety of humanity, but if you approach it and your cards with an open mind and willingness to learn, you will start to see -and feel - things in your cards that you are having trouble seeing now.
Set cards? No - that would be cheating. There could be any number of combinations which on the day might, or might not, tell you something exact and specific about the person in question.
As for it remaining a secret - why that more than anything else in the person's life? If someone consults, he/she must understand that things can show up in cards they might have been holding secret. That's not to say you blurt out to a guy in front of his wife: "I see you're a closet gay!" But I think that aspect - that tarot can throw up things that are hidden - all tarot readers should explain at the outset of a reading.
