If you can't be kind, at least be vague. - Judith Martin

DEAR MISS MANNERS:
When does a gentleman offer his arm to a lady as they are walking down the street together?

GENTLE READER:
Strictly speaking, only when he can be practical assisstance to her. That is, when the way is steep, dark, crowded, or puddle-y. However, it is rather a cozy juxtapostion, less comprising than walking hand in hand, and rather enjoyable for people who are fond of each other, so Miss Manners allows some leeway in interpreting what is of practical assisstance. One wouldn't want a lady to feel unloved walking down the street, any more than one would want her to fall of the curb.

Miss Manners’ mother always told her to travel either first or third class, but never second, when crossing. (Not crossing class lines, silly; crossing the Atlantic Ocean, in the days when that was done properly, with bouillon at eleven on the promenade deck and tea at five in the salon.) In first class, in those days, you had luxury; in third class, you had fun. This is the proper distribution of the world’s blessings. In second class, you had neither. Naturally, then, someone invented the one-class ship, where the advantages of second class could be enjoyed by all, which is probably why we have those overanxious things called airplanes for crossings these days.

Whenever possible, look at the camera, not at the person to whom you are talking. It represents the person to whom you are really talking: the viewer.