Pretty much everything I said about acceptance in my previous post on autism acceptance applies pretty straight-fowardly to other ways that people can be different from each other.
You don’t need to understand why someone is trans or how transition-related medicine works or how people make decisions about gender presentation to accept that your trans friend is who they are and deserves to be treated with respect. You don’t need to know all about trans issues to learn to use the name and pronoun someone asks you to use because that’s how to treat a person with respect. To accept someone trans as who they are requires you to trust them to be the expert on their own experiences and believe that they feel how they say they feel. If your friend says he feels happier with a different name, believe him and get on with using his new name. It makes him feel happier and all people deserve to be happy.
You don’t need to understand why some people are only attracted to people of one gender, why some are attracted to people of many genders and why some are attracted to nobody at all, to accept your friend with a different orientation from yours. If she says she loves her girlfriend, believe her. Trust that she is the expert on how she feels and what she wants, you’re not.
You don’t have to know whether or not there is a G-d or know very much about different religions or about atheism to accept that your friend has a different belief system from you. Trust them to be the expert on their own experiences.
This doesn’t just apply to your friends, but to everybody. To everybody you must learn to believe that they know better than anyone else what it feels like to be them and that they deserve to be treated with respect.
An example: I have a lot of disabled friends. Most of them, I have no idea what their impairment is and those who I do know I often know very little about that condition. We get along by believing people when they say they need help and helping in the way that is asked for. We believe each other when we say “I can’t do that” without needing an explanation of why or arguing.
Everyone is an expert on themselves. With very, very, very few exceptions you do not have a better idea of what a person needs than they do. Accept that people feel what they feel, want what they want and choose what they choose. Treat everyone with respect. We’re all only human.