You asked. A best-selling author and mom answered. From periods to body hair, we've rounded up some of Rosalind Wiseman's best advice for tweens and teens going through puberty. Have your own question? E-mail and your answer may appear in the magazine.

By Rosalind Wiseman

Q. My daughter is 11 and is the only one of her friends who has her period. She gets teased a lot, and she's horribly embarrassed. What can I do to help?

A. You're already doing something right if she felt comfortable enough to tell you what's going on. The first girl to get her period in a clique can stir up a lot of emotions among the other girls, who may be jealous and relieved, all at the same time. Girls often process these confusing feelings by targeting the person they think is causing the problem.

But knowing why someone is acting mean doesn't justify her bad behavior. Tell your daughter you're really sorry about the situation, and coach her to respond to her friends with something like, "Look, it's weird enough to get my period without being teased about it. I can't help that I got my period, and I can't control what you say. But it would be nice to have friends who'd make my life easier instead of harder. So please stop." You can also use this as an opportunity to share some of your own experiences at this age—just don't describe it exclusively as the most wondrous, magical time in a woman's life because she'll tune out.

Q. My 17-year-old son doesn't shower enough. Should I say something to him?

A. Here's a rule to follow when you want to talk to your son about something that makes you and/or him uncomfortable: Have the conversation side by side instead of face to face, maybe while driving in the car or watching TV. Then be direct: "Sam, I love you dearly, but you smell. You need to take showers more often. Every day before school would be ideal, but I'll be satisfied with once every other day." If he blows you off or seems to forget, I'd ask him straight up what's going on because his behavior may mean he's resigned to being rejected by his peers or he doesn't notice other people's reaction to him—maybe he's depressed or he has social skills deficits. Either way, if the problem continues, I'd get him the appropriate psychological help.

Q. My daughter said her volleyball coach suggested she lose some weight. Her doctor and I think she's fine. Should I speak to the coach?

A. It's hard not to want to scream at the coach about contributing to society's toxic messages to girls about being thin. But that's not good parenting. Speak with the coach in person (not by phone or e-mail) and ask him if he told your daughter to lose weight. If he did, request that he focus his comments solely on concrete ways to improve her game. If he didn't, discuss why your daughter has this impression and what he can do to address it. Usually I prefer for kids to advocate for themselves, but weight is such a sensitive and potentially humiliating issue that this is one of those times when you have to directly intervene.

Q. Our family is pretty strict about healthy eating, and I recently found junk food wrappers in my 10-year-old daughter's room. What do you advise?

A. Junk food isn't the issue here. The problem is she feels she has to conceal it. When kids sneak food it means you've got a control war—always a no-win situation. So say to your daughter: "I found a bunch of wrappers in your closet. I don't want you to feel you have to hide food. What's going on?" Then listen and reach a compromise. Maybe you and your daughter can find more appealing (to her) recipes to prepare together. And consider lightening up a little—high-quality chocolate eaten in moderation can be one of life's great joys.

Q. My son and daughter-in-law constantly nag their 10-year-old about what he eats and how much he weighs. I know this is not the best way to go about things. How can I help my grandson without stepping on too many toes?

A. You're right. Your grandson doesn't need nagging—or bribes, for that matter—but healthy family dinners and people who model eating slowly (so he learns to detect when his stomach is full). And he should engage in physical activities that allow him to achieve his correct weight as a natural consequence of the fun he's having. I realize you can't tell him this, but you can show him. Your grandson, at 10, is a prime candidate for a martial arts class. So why don't the two of you check out a couple of schools and enroll him in one for three months. Ideally, he'll like it so much his parents will pay for the classes after that. I used to teach karate, so just a few words on the kind of teacher (true for any coach) you're looking for: You want someone who encourages hard work, sets clear goals, and demands the kids support one another. And he should never brag about his own exploits or put students down because of their physical abilities or weight.

Q. My 9-year-old suddenly has very dark hair on her legs. Other girls have noticed, and she wants to shave. I think she's too young, but I don't want her to be teased either. What should we do?

A. This is a classic rite of passage for both of you. And I know it's tempting to say, "No way! Talk to me when you're 14!" But there are two things to keep in mind. One, most girls your daughter's age have absorbed cultural messages that tell them there are things "wrong" with their body that require fixing. Two, kids need all the help they can get navigating peer pressure. So explain to your daughter what's happening with her body because she's probably worried she's the only one going through it. Then discuss the pros and cons of shaving. Pro: She doesn't get teased. Con: She changes herself to please others. Your job is to help her realize when these decisions come at the price of her personal authenticity. If after all that, she still wants to, I'd compromise by letting her bleach her hair, and at 12 I'd let her shave. In the meantime, keep using body image issues like this one to teach her about making thoughtful choices.

Q. My teenage son recently decided to become an animal rights activist and a vegetarian. While I'm proud of his convictions, he makes dinner a nightmare with his comments. How do I get him to rein it in?

A. If he's really serious about educating his family, how about telling him to cut out the remarks and instead cook a meal that's in line with his activism? He can research good vegetarian recipes, go to the market with you, and help you cook. That way he backs up his activism by doing something beyond complaining. Of course this doesn't mean the family has to become vegetarian, but you should all make a good faith effort to try his food and skip the obnoxious comments and eye rolling.

Q. My 12-year-old stepson refuses to cut his hair, wash it regularly, or use a brush to keep it neat. My husband and I have even offered money or a trip to his favorite restaurant if he'll visit the barber. His mother is no help at all. Any ideas for us?

A. Realize a couple of things: It's his head and he thinks he looks good. And he's manipulating you and your husband—seriously, cash incentives? The boy is successfully pitting you and his dad against his mom. The best move here is to choose your battles. If I were you, I'd be happy with long, unruly hair, even if you can't see his eyes. You just want it clean. I'd say, "No more bribes and no more nagging to get your hair cut. Now that you're getting older and more mature, it's important to take care of yourself. So we expect you to shampoo every few days." When you refuse to play his games, and set limits clearly and without ambivalence, he'll be more likely to comply. What will seal the deal is peer pressure—it'll take only one negative comment from a girl to solve the problem completely.

Have your own question? E-mail and your answer may appear in the magazine.