Q: My sister-in-law drops into town from time to time, with or without husband and children, for a visit to her family. While here, she calls and invites herself to dinner. (The last time, she announced midway through the evening that she wanted to spend the night, due to her fear of night driving.) From the time she arrives until she leaves, the woman criticizes me relentlessly.

"Why do you quarter your potatoes so carefully? You're going to mash them anyway, just cut them and throw them into the pot." "I noticed you have velour towels. But why spend that much money on linens; terry cloth is more absorbent, and I've never spent more than $2 on a towel." "You're going to feed your dogs that chicken? Put it in the fridge and eat it in your next meal." "Why use butter? Margarine is so much cheaper. You can't really tell the difference in taste." "You should gain some weight, you're getting too skinny." (I'm a 7, and I work to stay a 7. I like being a 7, my husband likes me a 7. She's an 18.)

And on she goes, reciting a litany against our life style for the entire visit. She argues with and cuts down my brother and their children in front of us. She seems to delight in their obvious humiliation and embarrassment. By the time she leaves, we are frustrated and angry.

She is an outcast from the family--no one wants to be around her. I refuse to be drawn into an argument with her--yet I feel, as do others, as if I'm continually baited. I also don't want to be estranged from my brother's affection. My dad spoke to him once about her, and it only caused resentment.

So the problem remains--how do we handle this woman who attacks us in our home, and attacks other family members as well, during reunions in our parents' home? We are running out of cheeks to turn.

A. Many families are blessed with at least one person who knows exactly how life should be lived, down to the smallest detail, and is willing to share this knowledge without waiting for the ignorant and the timid to solicit advice. Be thankful that your family is not blessed with two such people, because their expertise is bound to conflict and the family turf becomes a battleground.

Miss Manners applauds your desire to endure, rather than exile, this fountain of knowledge, for the sake of maintaining cordial relations with your blood relatives under her immediate supervision. It will not be easy.

Here is a two-step method Miss Manners recommends for frustrating these spreaders of wisdom. (And you figured that Miss Manners was the one like that in her family, didn't you? Not nice. Miss Manners only gives solicited advice.)

First, ask the person for advice on everything. "What is the best way to cut up potatoes?" "Tell me the relative merits of different kinds of towels." "What do you think the dog would like for dinner?" and so on. You must ask before she volunteers, and you must offer no arguments--just listen, or pretend to listen, in silence.

Then ignore the advice. Don't say you are not going to follow it, but don't. If challenged reply, "Yes, I'm still thinking about that. Why was it again you thought margarine was better?"

This is one of Miss Manners' favorite faultlessly polite and cheerful ways to drive others into the madhouse.