Allies

Resources and advice for the friends, family members, and allies of nonbinary people. This also deals with some advice for getting along with and helping other kinds of transgender people, and some issues of concern to intersex people, too.

Etiquette

A lot of people forget their manners when they're talking to transgender people. Some allies think they mean well, but they say rude things to trans people that they would never say to cisgender people. This is just because most people haven't brought up with a good idea of the social protocol for some situations that are new to them. A lot of hurtful media has given people wrong ideas of what to do in these situations. For example, television shows where transgender women get asked intrusive questions give people the idea that this is what to do as soon as they find out that someone is transgender.

Use proper language and pronouns

This only applies to people who would like people to use gender-inclusive language, but otherwise, it is still more polite not to use language that would suggest a false gender.

For parents and friends of nonbinary people, it can be difficult to think of your friend or child as who they are, but you should try to think about them that way. When talking to oneself about another person, it is better for the person not to misgender them silently, since they will probably be more likely to speak incorrectly. A person who thinks of another as the wrong gender but tries not to misgender them is being dishonest and sneaky. If you think about your friend and child correctly and without delusion, it will prevent accidental or intentional misgendering, which will lessen their suffering. Imagine a world where everyone calls you by the wrong pronoun and labels you as the wrong gender, then everyone else who hears people talk about you assumes you are the gender associated with that pronoun and treats you that way. It would certainly be stressful.

Second, do not dare to use gender-specific language inappropriate to your friend/child's true identity behind their back. The first reason for this is the fact that it is simply impolite to talk about a person behind their back, and second, no one wants to give a bad impression of their friends. It is offensive to use gender-specific language which does not apply to a person, so do not do it.

Don't give unsolicited advice

Telling somebody what you think they should do, when they didn't ask you for your ideas, is always rude to anyone. It's common for people to do this as soon as they find out that their friend is transgender.

Don't give unsolicited fashion advice. If someone wants your opinion on how they look, they'll ask. It's always rude to tell any person how to change their looks if they haven't asked. If you have good fashion advice for nonbinary people, and none of them have asked, you can put it in this wiki on the clothing page.
Don't give unsolicited advice about how to pass as a certain gender presentation. As is often the case with unsolicited advice to anybody, this tends to be insulting rather than helpful.
Don't give unsolicited advice about surgery, or about things about their body that could be hard to change. This can be very offensive because it sounds like you're passing judgement on their bodies. Nobody likes to be treated like that. The person might not even be interested in changing or hearing about those things.

Respect their privacy

Private parts are private. If the nonbinary person isn't your patient or your lover, don't ask about their private parts, whether they've had surgery, or what gender they were assigned at birth. It's always rude to ask any person about their private parts, unless if you are their doctor or their lover. Some nonbinary people don't want everybody to know about that, or what gender they were assigned at birth.
Learn to be content with not knowing certain intimate details about all people, such as their private parts, or their gender assigned at birth, or what part of the gender binary you think they're the most like. If you start wondering about it, don't blurt it out. Put the thought away, and focus your attention on what people are saying and doing, instead of speculating about private parts of their lives. This is very important when having to do with people who you think look androgynous, who you aren't sure how to fit into a female or male category.
Don't violate confidences or "out" nonbinary people. It's always rude to spread information about a person that they don't want to make public. Some nonbinary people are very public and out. Others want some sensitive details to be kept private. That might include their gender assigned at birth, the name they had before they changed it, and so on. Your nonbinary friend might be out to some people, and not out to others. Let them decide how much they want to tell about themselves. Don't do it for them.
It's not helpful to introduce your nonbinary friend to others as being nonbinary. You might be outing them. Let your friend decide whether they want to be open about that to each person.
Don't gossip about your guess that someone you don't know well might be transgender or nonbinary.

Take up gender-inclusive things

When binary people take up things for themselves that are gender neutral or gender inclusive, this often isn't an example of cultural appropriation, but is an example of the "curb effect". Making a sidewalk curb accessible to wheelchair users makes a more usable street design for everybody else, too: people with baby carriages, shopping carts, and so on. The curb effect means any kind of change that society takes up to make life less hard on marginalized groups of people, making life easier for other people, too. Accessible design is good design. Gender inclusive things are a benefit to nonbinary people, as well as to binary transgender people, and to women of all kinds.

Take up a gender neutral title for yourself, such as Mx. This isn't appropriating from nonbinary people something that belongs only to them, because the Mx title is for anyone who doesn't want their title to tell their gender. Everyone has the right to leave their gender undisclosed. Ask organizations if they will let you or others to be listed under a Mx title in their paperwork. Also ask if they let people go without a title entirely.
When you introduce yourself, tell your name and pronouns. When you meet someone new, ask for their name and pronouns. This isn't appropriating from transgender people. It helps create a society that is friendly to transgender people if you make it standard etiquette to ask about someone's pronouns, rather than guessing someone's pronouns.