For me personally....
Don'ts; rice, pasta, bucketloads of sauce, and stay far, far away from the tomatosoup! (Last time I had that I had to excuse myself and take a brisk walk around the block to get my bs down. Felt so ill... But oh it was tasty, haha.). No noodle soups either... Though they might be able to leave the noodles out for you. Anything sweet & sour is problematic. Nothing fried in batter. Or, you know, moderately. I don't know how low carb you want to go! Stick with meats, meats and more meats, vegs too. Just scrape sauce off if you're not sure how carby it is. Unless you just ask for them to not pour sauce over the dish. Less messy, and less hassle while eating. You can just dig in. Me, I go over the menu before I eat out, so I know what to order. That has saved me from many a panic attack and drawing of blanks.
Most places have a menu online, so with some luck... Anything I'm not sure of, I'll google the nutritional values. But you can always ask to hold the sauce, replace rice with an extra serving of veggies etc... I had a really hard time asking for things, but I've found if you're polite enough about it and add a thousand thanks, which I usually do, any server will try to accomodate your wishes. (And my usual haunts know by now they're tipped well for their trouble). I skip family get-togethers sometimes when they go to a place where there is nothing on the menu I can eat or adjust.(They keep going there regardless. Thankfully it's the branch of the family I can do without, haha). But more often than not, after facing the first eating-out hurdle, it becomes easier, and most restaurants have workable options. Heck, you could even e-mail them and ask whether they'd mind accomodating you; give them a head's up so you don't have to explain loads at the table. Just don't miss out when you don't have to. Being a diabetic is hard enough as it is. Just be prepaired, and enjoy your dinner. Really. Because if you do miscalculate by accident, by god, it should have been worth it! (Like my farewell to the tomato soup, haha).