1Respect their gender identity. Think of them as the gender they refer to themselves as and refer to them with their chosen name and gender pronoun (regardless of their physical appearance) from now on. (Unless they are not out, or tell you otherwise. Ask to be sure if or when there are times it is not okay.)Ad
2Watch your past tense. When talking of the past try not to use phrases like "when you were a previous gender" or "born a man/woman," because many transgender people feel they have always been the gender they have come out to you as, but had to hide it for whatever reasons- or at least be aware of when you do it. Ask the transgender person how they would like to be referred to in the past tense. One solution is to avoid referencing gender when talking about the past by using other frames of reference, for instance "Last year", "When you were a child", "When you were in high school", etc. If you must reference the gender transition when talking about the past, say "before you shared your true gender", or "Before you began transitioning" (if applicable).
3Use language appropriate to the person's gender. Ask what pronouns the transgender person prefers to have used in reference to them and respect that choice. For example, someone who identifies as a woman may prefer feminine words and pronouns like she, her, actress, waitress, etc. A person who identifies as a man may prefer masculine terms like he, his, etc. Other transgender people have begun using gender neutral pronouns such as ze, zir, sie, hir, singular they, them, etc., but this is a personal preference.  Use the name they ask you to use.
- Your friend Jack has just come out as a transgender person, and now wishes to be called Mary. From this point on, you do not say "This is my friend Jack, I've known him since grade school." Instead, you say, "This is my friend Mary, I've known her since grade school." Table any awkwardness you feel for another time when you and Mary can talk privately. Definitely, if you want to remain friends, you will need to respect Mary's wishes and address her as who she is today, not the person you used to know; despite the fact that the transgender person IS the person you used to know, you just know them better now.
4Don't be afraid to ask questions. Some, but certainly not all transgender people will answer questions related their identity / gender. Don't expect the transgender person to be your sole educator, however. It is your responsibility to inform yourself. Also, if a trans person doesn't feel comfortable answering your question, don't try and "force it out of them." Lastly, questions about genitalia, surgeries, and former names should usually only be asked if you need to know in order to provide medical care, are engaging in a sexual relationship with the transgender person, or need the former name for legal documentation.
5Respect the transgender person's need for privacy. Do not out them without express permission. Telling people you are transgender is a very difficult decision, not made lightly. "Outing" them without their permission is a betrayal of trust and could possibly cost you your relationship with them. It may also put them at risk, depending on the situation, of losing a lot - or even being harmed. They will tell those they want to, if or when they are ready. This advice is appropriate for those who are living full-time or those who have not transitioned yet. For those living full-time in their proper gender role, very many will not want anyone who did not know them from before they transitioned to know them as any other than their current, i.e. proper, gender.
6Don't assume you know what the person's experience is. There are many different ways in which differences in gender identity are expressed. The idea of being "trapped in a man/woman's body", the belief that trans women are hyperfeminine/trans men are hypermasculine, and the belief that all trans people will seek hormones and surgery are all stereotypes that apply to some people and not to others. Be guided by what the person tells you about their own situation, and listen without preconceived notions. Do not impose theories you may have learned, or assume that the experience of other trans people you may know or have heard of is the same as that of the person in front of you. Don't assume that they are transitioning because of past trauma in their lives, or that they are changing genders as a way to escape from their bodies.
7Begin to recognize the difference between gender identity and sexuality. Do not assume that their gender correlates with their sexuality - it doesn't. There are straight, gay, lesbian, bisexual, questioning, and asexual transgender people. If the person comes out to you about their sexual orientation, use the terms they use.
8Treat transgender persons the same. While they may appreciate your extra attention to them, they don't particularly appreciate you making a big deal of them. After you are well-informed, make sure you're not going overboard. Transgender people have essentially the same personalities as they did before coming out. Treat them as you would anybody else.
- Be willing to listen. Many TG people live in small communities where sharing their experience is limited to their own kind. Often, being able to explain and educate people about their experience is helpful to both you and them.
- Don't obfuscate. If you are finding something difficult, let them know. An honest, straight forward response is a lot easier for them to deal with than cutting them off.
- Hang out with them. Make it "normal" - get used to them in the way they present and sooner or later you'll find that they aren't a strange person, they are "joe" or "josephine." You might just find you end up with a really good friend.
9Those who have begun to express a gender different from the one assigned at birth are usually undergoing a major life changing event. Patience, understanding, and a willingness to discuss issues these changes will bring about will help them through a difficult and emotional time. It is best to ask open ended questions that allow the person to share as much as they feel comfortable sharing. Examples: "How are things going?"; "You looked stressed. Care to share?"; "You look really happy. Something good happen?"; "How can I help support you during these changes?"; "I am all ears if there are things that wish to discuss."Ad
- Asking about trans peoples' genitals and how they have sex is not appropriate, in the same way that asking cisgender (those whose bodies naturally match their gender preference) people how they have sex is not appropriate.
- Not all transgender people pursue genital reconstruction surgery (GRS). GRS is almost always more appropriate to use than "sex change operation." Don't assume that it's appropriate to ask about a person's plans for surgery, hormones, and so forth, any more than you would pry into someone else's medical affairs. Moreover, don't assume that there is only one "right," path to transition (e.g. that to "really be transgender" or to "finish your transition," you need to have GRS).
- Some trans people will be comfortable answering questions, and some will not. If a trans person is uncomfortable answering, or doesn't want to, then let it go. If you need to know, use the resources below.
- If you slip up early on and say "she" or "he" when you meant the other, don't apologize too much, just follow the mistake with the right term and continue what you were saying.
- Many believe that the word "transgender" is an adjective, and a descriptive word; not a noun or a verb. Others believe otherwise. Just as you wouldn't call an older person "an old" or say they are "olded", it is inappropriate to refer to a transgender person as "a transgender" without adding "person", "woman", "man", or any other appropriate noun. Some transgender people also consider this objectifying and dehumanizing.
- Unless you have a close and personal relationship, it may be rude to ask what their "real" name or birth name was -- they consider the name they have chosen to suit their gender (if they have done so) to be their real name, and they want you to think of them that way.
- It has been widely accepted in the educational community (and others which deal with people with various disabilities/differences) that one not refer to people with their difference first, (i.e., transgender person), but that one refer to the person before the difference (i.e., person who is transgender). It might be a bit more clunky to articulate, but in the mind of the listener it identifies the subject of the communication as a human first and as different from others last. A small but important differentiation, in my opinion.
- Some people believe that the only "cure" for being transgender is to correct the physical appearance (with surgery and/or hormones) to match the mental gender identity. These people believe there is a problem with the body, not the mind. Current medical evidence and authorities support the effectiveness of these treatments (See AMA, APA, APA, NASW and WPATH statements.) Some people believe that it is society's gender expectations and limitations for men and women are the core issue and need to reflect an acceptance of a wider variety of gender expression for males and females.
- Gender Dysphoria is the term used by medical and psychological professionals and is the term used in DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th edition, May 2013). DSM-4 used the term Gender Identity Disorder (GID) but was replaced due to the pathologizing nature of the concept that Transgender is a “disorder”, not a natural part of the variation of human development, although only a small percentage of the population has this variation.
- Websites like My True Gender, PlanetOut or 4chan have transgender groups, or other sections for transgender people; go to them to talk to people or learn more.
- Never tell a transgender person that people will not understand or love them because of their transgender identity. It hurts very badly, and is not true. Many transgender people are understood, accepted and loved.
- Do not compare them to a non-transgender person by calling that person a "real" or "normal" girl/boy. What makes a man a "real" man or a woman a "real" woman is the way they identify themselves, not the way someone else experiences or classifies their body. A transgender man is no less a man than a cisgender man; a transgender woman is no less a woman than a cisgender woman.
- Avoid the use of transphobic slurs like "tranny" and "shemale." These terms are oppressive, objectifying, and dehumanizing.
- Even if you have objections to a person's transgender identity, you should always respect the person and never willfully embarrass them publicly. Embarrassing or humiliating the person does no good for anyone.This situation could also become unsafe for the transgender person.
- "Intersex" is a general term used for a variety of conditions in which a person is born with reproductive and/or sexual anatomy that doesn’t seem to fit the typical definitions of female or male,  While some intersex people are also transgender, the two are not the same and should not be conflated. 
- Be very careful when referring to someone's transgender identity as a "choice". Gender dysphoria is certainly not a choice by its very definition. Some transgender people describe their identity as a choice, and some do not. For some, the "choice" was to fix their body to match their mind. Find ways to respect a person's identity that don't hinge on whether or not they can "help it".