Never hesitate to ask in a restaurant. Ask TWICE because sometimes they won't know and won't trouble to find out.

I pay a lot of attention to the overall attitude of the restaurant. If it's the slightest bit of a problem, then I drop back to a safe position (eggs over easy, or a plain hamburger patty) and thank them for trying to find out (even if they don't.) The places that try to help know I'm not going to walk out with the entire party--I'm grateful they didn't do something to poison me.

I actually love walnuts, and make my pesto with pine nuts and a couple walnuts tossed in--or did until I found out a friend is allergic to walnuts. Now I don't mix them in anything, and clean the pan after working with them. Even walnut oil can set off a confirmed walnut allergy.