Disclaimer: I don't have Diabetes and I don't know everything about diabetes, but I did have gestational diabetes (GD) with my first pregnancy (controlled by diet and exercise - though it was touch and go for a bit, because my morning sugar and ketone numbers were awful).
The biggest thing I noticed, and I think "we" are all aware of it now with the onset of documentaries and anti-sugar propaganda, is how much sugar there is in everything. Like. EVERYTHING. It's obnoxious. When I had the GD, I transitioned (permanently - I had flirted with it before) to natural nut butters (peanut and/or almond) instead of their icing sugar filled counterparts, I stopped drinking juice (because WOW. I also stopped using juice when making smoothies. Always milk or almond milk for me. Water works too, I just like more vitamins, minerals, protein, etc. in my smoothies), I had already cut way down on any sodas, I started ordering thin crust pizza (because, honestly, I love the cheese and toppings more than the bread anyway), I started eating cottage cheese or plain yogurt (truth be told, I had to add a BIT of maple syrup to plain yogurt when I started, because it's foul. I still eat it every morning, but always over fruit and topped with granola and raisins), and I started really venturing into the lean proteins, grains, and fruits and veggies (emphasis on the veggies). I also make as much as I can - I bake muffins for snacks, I make granola, I make bread. SOME of that is because it's cost effective, especially when I'm packing lunches for at least three people, but most of it is that I can control what goes into these things, and (thus) what goes into me. Mostly, it's the sugar content that I'm concerned about (so I'll also edit recipes to lower the sugar, and/or use maple syrup or honey where applicable).
ANYWAY. Long ramble, short: I think a huge thing you can do is make sure you know what kind and how much sugar is in your day-to-day foods. The more you can make, the better you'll be, overall. (And there are some great cookbooks and magazines out there regarding diabetes. Better Homes and Gardens usually does an awesome Special Interest publication on diabetes and recipes for it. I have a few of those issues and I've loved them.)