Don't do some of the things I did when my first transition failed (or rather what led to the failure of my first transition). Here's a couple things I figured out the second time around (in no particular order):
1.
Resist the urge to DIY. The urge is strong and there are plenty of websites more then happy to help you achieve that goal. I'm not going to BS you and tell you "hormones are pretty powerful stuff", the real truth is (and I say this having DIYed 2 or 3 times in the past) hormones change how you feel about just about everything. Its important to have someone to talk to about those things. They also take an incredible toll on your body and that needs medical monitoring. Not to mention that medicine is more of an art then it is a science and what works for one person, works for that person only. Without medical monitoring you're either wasting money overdoing it or wasting money on drugs that aren't doing anything but stressing your liver.
2. Pretty much everything in your life will change between now and then. I'm still working through this part, but the fact is people have to transition with you or they have to leave your life (either their choice or yours). You need to build up your support network and accept that the people in your life you love and trust as the boy they believe you to be may not be as positive a part of your life as you shift from boy to girl.
3. Your mother probably told you, "you get more flies with honey than you do with vinegar". She's right. If you want to fast track to failure, be angry with the world, be in your face about being angry with the world. Throw around ultimatims, demand things of the people in your life. In short, push the people that love you out of your life if they show any resistance on their own path to accepting who you are becoming. Some people in your life need to leave, but work towards understanding with them before you cut all ties.
4. Fight the unnecessary depression over all the things you didn't get to do growing up as a girl. We all have to grieve for our lost childhoods, but don't grieve over never being the prom queen, the cheerleader, or any of the other popular girl stereotypes. Most cis girls didn't have that experience growing up either.*
5. Most of all, know who you are, the girl you can be, and go after that with everything you can. This too takes acceptance though. No one is too tall, too fat, too anything to not transition. However, not everyone can be the prom queen, the cheerleader or the girly girl. If tomboy, girl jock or even stone butch lesbian works for you - own it!
6. Listen twice as much as you talk. Listen twice as much as you probably think you should. Ask lots of questions. Every other transitioner is either an example of what to do or what not to do, learn from all of us. Give back to the others that will come after you, whether they're 6 or 60 when they first walk the path.
That's about all I can think of for now.
* My revelation was getting depressed watching kids play on the beach. Who does that? I told my therapist that's when I finally understood things, that I would have given anything to be a girl. Growing up a boy was difficult for me, at best, I did things I hated doing just to try to fit in as the boy I wasn't. Would I have not done those things as a girl? Probably not, but I would have felt alot differently about it, or at least not felt the pressure to do things I didn't want to do. I compared it to a stereo being stuck on static. I would have given anything just to turn down the noise that was my gender dysphoria. More then not being seen as female, I feared having to live the rest of my life as male.
