Nothing bad happened, but my husband did get caught taking a bowl of cereal upstairs when we were visiting my sister Claire at her home in New Jersey.

"We're not allowed to take food upstairs?" I said to Claire, all worried and apologetic.

"It's fine," she assured me. "We don't do it, but it's fine!"

Then there was the issue of putting away leftovers. To me, if you have two slices of pizza to save, and if both are sitting on the piece of aluminum foil that you used underneath them in the oven, you simply wrap the foil around the slices, scrunch the sides, and place that tidy package in the refrigerator.

But Claire lives in a total Tupperware house, and so after I did my foil bit, her husband, James, quietly took out the pizza and unwrapped it and redid my work with the use of a flat sandwich-size container.

He didn't complain, and I am not complaining. We all get along great. But it's hard, when you're a houseguest, to just automatically understand the etiquette of the house. Staying at Claire's for a few days, and before that at my friend Marie's, and before that at my parents', I wondered why there aren't commonly accepted rules of etiquette for houseguests in the way there are for people who attend fancy dinners and must choose between many forks.

Is it okay to sample your host's shampoo in the shower? Should you ask first? My general rule of thumb, which I am only now discovering I even have, is that if it's family you have free rein with personal care products, but if it's not you don't. But Marie has been my friend since high school, and in college she slept at the bottom of my dorm bed like a little cat, and so in her shower I found myself reaching for that yummy strawberry-kiwi goo without even thinking. Now I think I should have thought.

Also, was it okay for me to just go in the closet and grab towels? And should I have kept better track of my towel usage? I could go on and on about linens. Should you strip the bed before you leave? Where exactly should you put that lump of your used sheets? Should you offer to make up the bed with fresh linens or is this getting too personal?

Personal. That's the thing. When you're a houseguest, you witness a family's personal habits and expose your own. (Read: The husband needs his cereal before bed.) The amount of coffee I drink in the morning is embarrassing when you put it up against that of a person who brews a six-cup pot for a whole gang. "You mind if I make a little more coffee?" I said, at each of the three homes I've just returned from. Then I felt a need to actually block the view so no one could see how very many scoops I was putting in. And then I felt a moral obligation to sneak out to the grocery store so as to surreptitiously replenish the supply.

My dad is a man with a place for everything, so I try to make sure to always hang the front door key up on the little nail provided, but sometimes I forget and then things start going downhill. My mom is a woman who gets bothered by nothing, absolutely nothing, except for my father when he's bothered. So now, when I check my e-mail on my dad's computer, I forgo the urge to defrag his hard drive, because the last time I tinkered, it all went kaput. This, I think, is a good basic rule for all houseguests. If you must use the family computer, keep it simple.

When Claire stayed at my house last summer, she kept commenting on how there was "so much to look at!" I am only now coming to understand that she must have meant the mess. Neither she nor Marie nor my parents have piles of old magazines and catalogues in every room that you can dig into if you need a little easy entertainment. "Don't you people read?" I found myself thinking at Claire's, and then I saw my daughter running around the house with a handful of worms she had collected outside, so I quickly escorted her out. "I don't think we're allowed to do that here, honey," I said. Not that we have worms inside our house either, but that wasn't the point.

When you're a houseguest, you don't want to pull surprises. You want to be neat. You want to be courteous. You don't want to show any outlandish behaviors. But you can't possibly be expected to know the etiquette of each house (forgive your husband for that upstairs cereal bowl!), because nothing so personal can ever be generalized. It would take years to learn all the ins and outs of just one house. And, as Benjamin Franklin reminds us with what is perhaps the only lasting piece of houseguest advice ("fish and visitors stink in three days"), you just don't have that much time.

Jeanne Marie Laskas's e-mail address is post@jmlaskas.com.