I would write down some of my most burning questions, because you will be getting a lot of information thrown at you, then by the end of the appointment, if those questions haven't been answered, you can have the endo address them.
Also, you probably want to leave with some goals to work on. Things like fasting and post-prandial (after meal) BGs, improving A1C measurements (an average measure of how you've done over the previous 90 days), testing frequency, meal planning, etc.
The most important thing to remember is that you are in charge. Your endo is the expert consultant you have hired to make recommendations. At first, you will want to follow those recommendations as precisely as possible, but when you next meet your endo, part of your discussion should be which recommendations are working for you and which aren't, along with how to adjust the recommendations to help achieve better health outcomes for you.