Start a food diary now, it will be part of what you have to do once you've been seen so you may as well start.
The advice generally is to go on a low GI diet, you can have carbs but small portions and complex not simple carbs, you also need to pair them with protein.
For example get the small loaves of whole grain seeded bread, 1 slice of toast with scrambled egg, or bacon, or peanut butter.
It helps to not snack in the evening, that gives a nice big window without any sugars for your body to regulate and helps your early morning sugars.
For snacks during the day you want to be having veg instead of fruit and looking for high protein options, things like cheese strings, chunks of chicken.
Don't skimp on good quality fat, it's great for filling you up, reducing the need to snack and regulating your sugars, so full fat Greek yoghurt is so much better than a muller light (I had my highest sugar reading ever 2 hrs after a muller light!).
It's not a calorie controlled diet, so you do not have to be hungry or restrict yourself, you just have to look for alternatives. You could have a great big plate of sausage, bacon, mushrooms, grilled tomatoes, eggs. Just don't have the hash brown or fried bread.
If you like jacket potatoes, try baked sweet potato instead, lower carb and load it with a high protein filling like tuna or full fat cottage cheese.