To be fair to straight readers, when characters have straight relationships, the writers are completely unambiguous about it. They kiss on panel, refer to their relationship, and talk openly about it.
On the other hand, an awful lot of LGBT characterisation is subtexty, or subtle or off panel. I know a lot of that is historical, where legally in the past creators couldn't openly portray same sex relationships so they hinted at them; but that leaves things open to interpretation. (When I was a kid, I thought Mystique and Destiny were just good friends for example, and for a long time there was nothing definitive on panel which said they weren't).
I'm still not 100% sure if Storm and Yukio were lovers. On balance, I think Claremont probably wanted you to infer that they were, but it's never been made 100% clear.
Even now, gay relationships are hinted at, whereas straight ones would just be shown. The Northstar/ Hercules scene is a good example. Pak has said in interviews that he intended it to be read as Northstar and Hercules had had an encounter, but it's written in a way that is ambiguous, and even worse Northstar who is out and proud as a gay man acts ashamed. ( I loved Incredible Hercules as a whole, but that was a crappy scene). Now Alonso comes out and denies it ever happened. The whole thing is a bad message.
So to answer the OPs question, part of what it takes is simple, unambiguous, on panel evidence; like how straight relationships are approached. enough with the hinting and the furtiveness.