I like using action statements more.
"I am transgender. Which means I've always been uncomfortable as a guy, and now I'm going to stop trying to be a guy anymore. It's not your fault, it's just who I am and how I feel. You are very important to me, and I'd like to retain your support/friendship..."
etc.
The more you are definitive and clear with your language, the easier it will be for them to know how to react to your statements. If you can be calm as well, that helps too. People react more to your body language and tone than your words anyway. If you can come out to yourself in the mirror, you can practice having a confident open posture. Eye-contact is also an important aspect as well. People are much less likely to argue with you about something you are an expert about. If you appear confident, they will defer to your judgement a lot of the time. But they will likely have a lot of questions, be prepared to answer them.
One of the questions I got each time was about my sexual orientation. If you aren't prepared to be definitive about saying you'll heterosexual (attracted to men), or lesbian, explain that you'll figure it out later, once you are more comfortable in your own skin.
Second was how far I was planning on going. For your parents I'd suggest not telling all the plans for transition, it can be overwhelming. But once you are comfortable telling people, you can just tell them as much as you are willing to reveal. When I told my best friend, I didn't hesitate before telling him I'm planning on going through it all. But you can usually judge how well the conversation is going by the way the other person is reacting to the lead up to the more complicated questions. If it is not going well, just tell them you wanted to tell them and then give them time to collect their thoughts so you can discuss it more with them at a later time, then you gtfo.
Hugs,
- Katie