You know it's not cool to smoke and swear in front of your children. But watching television? "If you want them to be active, you can't just order your children to go play while you watch TV," explains Carrie Contey, Ph.D., a clinical psychologist and parenting expert. (Find Out: What Type of Parent Are You?)

Just as your kids learn how to speak by listening to the sound of your voice, they learn how to live by observing your actions, Contey says. And even if you exercise every day, unless your kids see you working out--or at least putting on your workout gear and heading out the door--they won't understand that it's part of your routine. "If you come home every night and immediately turn on the television, they're going to assume that's what you're doing the rest of the day, too," Contey adds. And so they'll want to do that--and only that--themselves. Save your TV time for the hour or two after you've put the tykes to bed--when they won't see it, she advises. And try to go outside with them as much as possible to show them that you love physical activity as much as you hope they will.

Apart from your boob-tube habit, what else are you doing that may be bad for your kids?

Telling white lies.
A cop pulls you over for speeding, and you tell him you were rushing to get your daughter to soccer practice--even though she's in the back seat and knows that isn't true. Lying is such a commonplace practice in an adult's life that you may not even realize you're doing it, says Alyson Schäfer, a psychotherapist and author of Honey, I Wrecked the Kids. But your child will know. And, following your example, she'll assume it's no big deal to fib even about big stuff.

Keeping secrets from your wife.
You swing by McDonald's for a snack and whisper to your child, "Mom doesn't have to know we snuck out for some fries." You may think your deception is harmless-or even a type of parent-child bonding. But you're demonstrating to your kid that it's okay to lie to your partner, and you're undermining her authority, Schäfer says.

Teasing your tyke.
With other grownups or your partner around, it may seem fun to employ a little sarcasm or gentle teasing--say, telling your son he'll turn into a watermelon if he swallows a watermelon seed. But he won't understand you're not serious, Contey says. Kids are achingly literal, all the time. You need to be as well, she adds.

Spending too much time on your iPad.
If you're fine with your child having a cell phone at age 6--and playing with a tablet before he can walk--then feel free to thumb away on both, Contey says. But if you want him to spend his early years with books and hands-on activities like Legos, you need to put down your own digital devices when he's with you, she explains.

Losing your temper.
This includes losing it with anything or anybody--not just your kids. "Children tend to believe any bad things that happen are their fault," explains Susan Newman, Ph.D., a child psychologist and author of Parenting an Only Child. Even if you're pissed because your favorite team just blew a lead, your child will assume you're upset about something he did, which will frighten him.

Making fun of a crazy friend or annoying relative.
An offhand crack about "your cousin the drunk" or "your loser friend from college" will imprint itself on your son's brain, Newman says. And he's liable to repeat it the next time you're around the person you good-naturedly insulted, she adds.

Joking about your kid's teacher or school.
You can probably recall one or two oddball teachers from your elementary school days. But while you may think it's harmless to poke fun at your child's zany science teacher, he will assume you don't have respect for that person--or for school in general. And so he won't either, Schäfer warns.