THE HAT is dead, Miss Manners was informed some years ago. She heard it from the same people who announced, at various times, the death of the theater, formal weddings, living in the city, the fountain pen, handicrafts, having babies and even -- would you believe it? -- good manners. Miss Manners does not rush out and send flowers when she hears such an announcement.

Etiquette question: When is it appropriate to send flowers to a hat?

No, no, that's not it at all.The question, Miss Manners has concluded from looking about her, is when to wear a hat, when to take it off, and what type of hat to wear. This information, once known to every man, woman and baby bonnet, seems to have blown away during the hatless era.

Ladies wear hats to luncheon, teas, weddings, christenings, funerals and other religious services. This would not be difficult if the rule were observed that a lady never goes outside her own door in daylight without a hat. (Inching out as far as the sidewalk to retrieve the newspaper doesn't count.) The only excuse for wearing a hat inside one's own home is that one has spotted someone coming up the walk to whom one plans to say, "Oh, I was just on my way out."

Daytime hats are worn during the daytime, oddly enough, and evening hats may be worn during the evening. The difference is that a daytime hat, which is apt to be made of felt, velvet or fur for fall or winter-time wear, or straw for spring or summer, should look as if it settled on the head on purpose.

Evening hats should look like giddy, tiny collections of merry scraps -- a sequin, a feather, a bit of veiling -- that were wafting aimlessly through the air when they naughtily decided to perch somewhere, just for fun.

Ladies' hats are never checked at restaurants, and they never go to the theater at all, unless they look like bathing caps gone formal. As a matter of fact, ladies should never remove their hats until they get home, any more than they would remove their other clothes. (Miss Manners does not wish to argue probabilities here.)

Gentlemen behave quite differently, as you may know. They remove their hats to show respect, when they are addressing ladies or entering houses, clubs or elevators. They cover their heads in synagogues, but not in churches.

Raising the hat is a gesture performed only toward strangers, to accompany or represent an apology or expression of gratitude amid the bustle of public life. Tipping the hat is the quick gesture of someone, such as a polite cab driver, who expects a tip.

With business suits, gentlemen wear gray or brown felt fedora, derby hats or black Homburgs, or in summer panama or straw hats. With the most formal morning dress, they wear black silk top hats, and with the less formal sack coat, black derbys. In the evening, they wear black Homburgs with black tie or high silk hats or collapsible opera hats.

Gentlemen must remember to make flirtatious comments to ladies about their hats, but never jokes about the probable cost.

Do not bother to inform Miss Manners that the hats you have observed being worn in cities these days are all cowboy hats, motorcycle helmets, ski masks or Mickey Mouse ears. First we establish the principle, then we learn the manners, and then we get the proper equipment. MISS MANNERS RESPONDS

Q. Tell me how to give condolence and congratulations at the same time, without making a mess of both. A friend of mine did so badly in this same case that she's refusing to go out in daylight any more.

The case is this: Another friend has been trying for many years to have a baby. Has she ever been trying! We've heard all about her operations, her husband's sperm counts, everything. Every time she sees a pregnant woman on the street she looks at her so greedily I feel like telling the lady to hang on to what she's got. They even considered having her husband get someone else pregnant and then take the baby home.

Last summer, my friend's brother and sister-in-law were killed in an accident. The baby was miraculously unhurt. So of course my friend not only has her baby now, but it's one who is closely related to her.

Now, my other friend went over to see the baby, bringing it a nice present, and so on. The new mother was all shining and radiant and smiles, so what did our friend say to her? "Wow, weren't you lucky?"

Fortunately, I was away when all these events happened, and this fall I have put off seeing my friend for fear of doing something similar. I am going to sit here waiting until you tell me what to say.

A. The trick is to deal with these events in the order in which they happened. This will also suggest the proper point of view.

"I was so sorry to hear about your brother and sister-in-law," is the first message you deliver. Then you can mention the baby, taking care to express the poor child's luck in finding such a marvelous home. Notice what service the adjectives do in that sentence.

Q. I am being married for the second time, and I want everything to be in good taste, but I'd like it to be bridal, too, as this is going to be it. I will be wearing a pale blue velveteen dress, not a big white wedding dress. But is it all right to have a big white wedding cake?

A. Certainly, assuming that the cake has never been served before.

Feeling incorrect? Address your etiquette questions (in black or blue-black ink on white writing paper) to Miss Manners, in care of The Washington Post.