I am hooking back up with my ex who says that she still has feelings for me.
This girl is your ex. That means you used to date her. And if you used to date her, then I'm betting that would mean you talked to her on a regular basis at that time. You're relying far too much on somebody giving you a set of guidelines, of rules to follow to ensure you a 100% success rate.
Sure, you probably screwed things up with this girl back in your AFC days. And you know what? The rate your going, you're doomed to f*ck up again with this.
You are far too concerned with screwing things up with this girl. That's all she is, a little girl in high school. This isn't rocket science. This isn't even a complicated situation. The only way to guarantee your own failure, is to overanalyze the situation like you've been doing, and worry about the right things to say to impress her.
You ask how to talk to her on the phone?
DON'T WORRY ABOUT IT!
Who gives a f*ck what she thinks?! For one, she's your ex-girlfriend! What good is an ex-girlfriend? I'll tell you! No good! You should be out finding new women! This girl is probably your ex for a very good reason, and now your thinking about giving it a second try?
How about trying something different? Move on with your life, focus on yourself, and don't worry so much about pleasing a god damn chick. There will be many more of them in your life time yet, worrying about how one of them in high school will react to you will get you nowheres.
The only way your skill as a Don Juan will grow, is if you go out, grab your balls, and gain some real life experience. No amount of reading, posting, and debating will help you. You'll have the knowledge, but you won't have a clue what to do with it.
There's only thing you can do in this situation. And that's to just do it. Call her. Meet other girls. Have fun.
Just live your f*cking life.