What you do depends very much on what kind of insulin you are taking. If you get exercise lows from lantus the best thing to do is to eat a snack containing carbs before you work out. Although this seems counter productive, it does not have to be an unhealthy snack..a banana works great. Because you can't change the lantus dose once you take it you have to fix this with carbs.
If fast acting insulin is the issue then you can take less with the meal before you exercise.
I like to use gatorade for lows, or to prevent lows during exercise. The little 12 ounce bottles have 22 carbs, but I find they do not raise my blood sugar too much or cause a high later. I always have 2 of these by my bed, 2 in my gym bag etc. If anyone is concerned about how things "look" on your treadmill at the gym, nobody would think twice about you having a sports drink there.
Mostly it is trial and error and seeing what works for you. I workout everyday and I still do a lot of trial and error.
It is great that you are trying to figure everything out in advance. Try to relax until your doctor's appointment. You might think you have it all figured out and then he might have a whole different plan for you.
alisa