I remove my hat when I go inside any building, excluding any "open" buildings, train stations and similar, supermarkets and similar (but, as Wolfwood also said, I remove my hat in smaller stores, generally a one-off local store).
If I go to a fast-food restaurant to buy food to take away, I'd leave my hat on. If I'm going to eat there, I'd take it off when I sit down. I just can't eat with a hat on, it just feels wrong to me. Even if I'm eating outside. The only exception to this would be my panama, which I wear when having picnics, etc.
Exceptions kick in at appropriate times (if my hands are full, if I'm only popping into somewhere for a few minutes, if there is nowhere at all to put my hat, etc.)
If I go to a fast-food restaurant to buy food to take away, I'd leave my hat on. If I'm going to eat there, I'd take it off when I sit down. I just can't eat with a hat on, it just feels wrong to me. Even if I'm eating outside. The only exception to this would be my panama, which I wear when having picnics, etc.
Exceptions kick in at appropriate times (if my hands are full, if I'm only popping into somewhere for a few minutes, if there is nowhere at all to put my hat, etc.)