Look at your audience. For some people it may not make sense to come out. For instance a person under the age of 18 may have a harder time with this process due to being a minor and dependent on family members still. It may be smarter to confide in a trustworthy friend or two before going to the parents. Some family members and friends may be more willing to be your allies than others. Start with a brother, cousin, or a friend whom you can trust.
Do some research. Arm yourself with knowledge in case a loved one has questions and to make your coming out methods as informed as possible.
Write a letter. Composing a letter to your family, friends, and loved ones can help ease the tension created by perceived rejection. Be clear on why you are transitioning and reaffirm the importance of this process. This can be used to come out to family members you rarely talk to or see. Use letter from others to get ideas on how to address your loved ones.
Provide reading material. Literature on the transgendered community may help those whose loved ones are drawn to reading material. This can give a lot of information to a person without you having to interact with the individual a great deal. Many organizations have brochures and pamphlets full of information. Contact your local Lesbian, Gay, Bisexual, Transgender organization to ask about procuring a few to give as support material. Quite a few books have been published on the transgender community. Review a couple and pick the one that's best for your situation.
Sit down and talk about it. Being open and direct is a tactic that can earn many points with relatives and friends. This gives them a chance to ask questions and, while you may not always have the answers, you can be honest about your desire to transition or identify as transgendered.
Be patient. This isn't going to all happen over night. Coming out is a longer process that may take a lifetime. You can get the important people notified, but you may always be running into acquaintances and people from an earlier time in your life.
Be confident. Knowing that you identify as transgender and may need to take action in some way, shape, form, or fashion is a position that you need to be clear on. Speak clearly and firmly, but be responsive and flexible.
Choose your friends wisely. Coming out to an untrustworthy friend may make the process harder than it needs to be.
Search for example letters to get a good idea of what one may look like. Use the letter as a framework and tailor it to your needs.
Plan your discussion time accordingly so you wont be interrupted and will have ample time for questions.
Read literature ahead of time. Marking in the margins of books or highlighting may help you collect your thoughts and show you are serious.
This may cause some family and friends to not want to talk to you. Unfortunately this is a by product of ignorance and resistance to change.