Amy Herring has had enough of parents neglecting to R.S.V.P. for birthday parties for her three kids. It has happened so often that she now writes "call for directions" on invitations, so parents have to call if they want their children to attend.

Cindy Birmingham's pet peeve is parents who don't control their small children while gifts are opened. "The birthday child is surrounded by kids ripping at his/her presents," she says via e-mail. "It makes me NUTS!"

But Christina Brockett's story takes the cake. While hosting her son's sixth birthday party at a small theater, she was greeted by a father who hadn't R.S.V.P'd. He arrived after the party had begun, toting his 6-year-old and an uninvited 3-year-old sibling. Brockett was surprised to see them, but she welcomed both kids to the party.

"As I'm doing that," she says, "he is just kind of like, 'OK, see ya later,' and he leaves." Brockett laughs about it now, but at the time she was frustrated at having to feed and watch over two unexpected guests while hosting a large party in a public place.

In this age of hyper-planned children's parties, it's not just the kid who pokes his finger in the frosting who has become a party pooper -- it's his parents, too.

Occasional etiquette missteps are usually greeted with patience. Busy parents don't expect perfection from one another. But serial offenders have some parents steaming, a situation that puts their kids in an awkward position.

If you're a parent or grandparent who spends time on the kid party circuit, here are some thoughts from the experts on how to navigate this social scene.

To stay or not

Parties often happen in public places, such as bowling alleys or gyms for kids. It's a less controlled environment than a private home, so parents of small kids usually stay.

Is that expected?

Kate Lawler, executive editor of Parents magazine, says it depends on age: "We generally say that 4 is old enough for the parent to bring a kid to a party and then come back when the party is over." The key is asking the host whether they'd prefer you stay or go.

Greg Byrnes and Craig Handleman, co-founders of the social networking and information site ParentSociety.com, agree that the answer is age-specific. But they set the bar closer to age 6, as do readers at BabyCenter.com.

It's best to call in advance to ask what the hosts prefer. If they didn't plan to feed a dozen parents, it may be a problem if everybody stays. And yet, Byrnes says, you don't want to get branded as someone who drops and dashes with hardly a word.

Sibling tag-alongs

Should you take siblings along to the party? No, say the experts, unless they were explicitly invited.

Party events are often priced per child, so extra kids mean extra expense for the host. Also, the party space may not be childproof, and the presence of extra kids can make a frenetic party tip into chaos. Talk to the host if you can't leave a sibling behind.

The giving tree

Is there pressure to take an expensive gift? Experts say it's always fine to take a simple, age-appropriate present, even if the party is extravagant.

A recent poll of more than 1,600 BabyCenter readers found that 17 percent specified "no gifts" on invitations to their child's party or said gifts were optional. But the majority of readers, Murray says, spend $15 to $30 on a gift.

You're not expected to give a gift if you decline an invitation, Lawler says.

The keys to this social landscape, Lawler says, are common sense and plenty of communication with your hosts about their plans and what they expect from you. And, she adds, don't forget to R.S.V.P.: "It seems obvious, but people do forget."

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