1. "I'm not trans-phobic, I just don't support their lifestyle."
This is the most ridiculous thing I have ever heard someone say. If you don't support trans people, you're most likely trans-phobic, plain and simple. It's just another way of saying 'hate the sin, love the sinner', and we all know how offensive that is.
2. "He/she was born a girl/boy."
I wasn't 'born a girl.' I was born a boy and was labeled a girl and I'm sure a lot of other trans people wouldn't take too kindly to you telling people that they're trans. If someone wants to tell people that they had transitioned, they can tell the person themselves.
3. "But you made such a wonderful boy/girl!"
Honestly, anyone who ever says this should never talk to me again. Not only is it outright insulting, you could really hurt someone. I know that every time my parents talk about how I looked before I could buy a binder my dysphoria flares up and I've seen that it happens to a lot of others.
4. "Oh, I'm so sorry! I'm such scum! You must hate me so much for misgendering you!"
It really irks me when people act up and try to make you feel bad for them for misgendering you. They're just making it about them and half the time it isn't even sincere. Its almost always in the middle of a conversation, too, so it throws it completely off track.
5. "Can I just call you __ instead? Its what I know you by!"
If someone wanted you to call them by their old name, they would have told you. If someone says "Hey, can you start calling me ___?", you should call them what they tell you. If you really care about a person you should call them by the name they request.