If you're a type 2, like me - (I should add here that I don't take medication)...
I begin fixing a breakfast that includes healthy protein, fat, and low carb vegetables as soon as I get up to avoid the unwanted "liver dump" of glucose into my bloodstream in the morning.
Delaying eating for up to 5 hours sometimes is helpful (when blood glucose levels are unusually high). This is easier to do on the low carbohydrate diet, and more possible on days off than work days, of course.
Walking an hour and a half after a meal, even if only for 1 mile is the most helpful of all the strategies I use. If a blood glucose level is unusually high, I need to walk 2 miles.
When my blood glucose levels start trending up, I'm more careful about what I eat until they trend back down and I maintain lower readings for a few days. But this isn't always possible due to work and stress. I do what I can when I can.
Fasting 12 hours between dinner and breakfast most days helps too - (I try not to eat 3 hours before bed; if I really need a snack, ten green olives with pimentos removed usually does the trick).
Testing a minimum of 2 hours post each meal keeps me aware of what's happening with my body. I don't know how anyone managed their blood glucose levels prior to having access to glucose meters.