Response to Tim Walters
There are things cis allies can do to help.
If you see harassment happening, get between the abuser and the person. Ignore the abuser entirely, and engage the targeted person in some trivial conversation - turning the focus away from the abuser.
Or, bolder, confront the abuser directly.
2) Provide safe haven
Let the harassed person know that they can always call you | crash at your place | count on you for backup | whatever level of support you can comfortably provide.
3) Be vocal about your views. (Don't proclaim your allyship, centering you, but speak out against bigotry and for LGBTQIA rights.
4) Make the person's spaces safer. Enforce use of correct pronouns, thus removing that burden from the targeted person. Make it known your spaces are queer-inclusive. Hand a flag, or some way indicate you support queer folx.
5) there are other ways. Feel free to think up your own. Volunteer, write to congresspeople. staff a hotline, etc. etc.