I've started preparations, but haven't actually started yet. I do feel the wisdom of age has finally caught up to me enough to offer advice though.
Don't rush into things. I used to spend hours a day looking for ways around the system, looking at it as having to jump through hoops. Wondering why, if it's considered cosmetic surgery, I can't just elect to do it without having to put myself in danger on the way.
Now that I'm older, I'm glad I never jumped the gun, although at the same time, I wish I had started earlier. I see a need for a RLT now where before I believed that I needed SRS in order to feel safe in the RLT. Without living every aspect of your life as the opposite sex for long enough to have had doubts during it, you are really only guessing that you'd be happier as the opposite sex. That's a lot of heartache and expense to commit to on a hunch. Give yourself time to get things figured out, like voice, gender queues, your own personal style, income, etc.