I don't go out to restaurants very often, but when I do I usually order something that is pretty much primal anyway, like steak or grilled salmon. I ask to replace white potato with either veggies or sweet potato. I eat out so rarely that I don't really bother to ask what kind of oil or fat my meat has been cooked in, although I probably should.
My sister-in-law on the other hand is gluten sensitive, so she and my brother will only eat at restaurants that have a dedicated gluten free menu, and even then she asks a bunch of questions to make sure there will be no cross contamination. No place has ever had a problem catering to her needs, and are usually very happy to do so. So don't be afraid to make special requests, it happens all the time and restaurants are used to it for the most part.