It’s trans men and trans women, not transmen and transwomen—trans is an adjective that answers “what kind of men/women"—cis works the same way
Never call trans men FTMs or trans women MTFs without their permission
Trans is short for transgender, it’s not plural for anything—trans person and trans people are both correct
Never use “born in the wrong body” or “used to be a boy and became a girl” or “biologically/genetically male/female”—all are just fancy ways to misgender someone (self identification with these phrases is different)
Transgendered is wrong, so is “a transgender” and “transgenders”
Being trans is not a sexuality nor is it a “sexual disorder” or any kind of disorder at all—gender identity disorder is not a real thing, and being trans isn’t a medical condition
“Transsexual” is generally considered an offensive term and should never be used to describe someone without their permission
Don’t refer to a trans person’s gender as their gender identity, it’s just their gender
Similarly don’t refer to their pronouns as “preferred pronouns"—they’re not preferred, they’re mandatory