Show, Don't Tell
You're chatting with a potential new-mom friend at the playground when suddenly her toddler lets out a howl. You turn to see your own 20-month-old pulling on the other child's hair as if it were the pay-dirt string on a birthday pinata. You rush over, separate the kids, and sternly admonish, "No pull hair! No pull hair!"
The Problem: Your daughter hears "pull hair, pull hair!" -- precisely what you don't want her to do -- and still may not understand what she should do instead.
The Fix: Take her hand while saying, "Gentle touch, gentle touch," and help her to softly stroke your own hair. "When it comes to discipline, children this age understand actions and energy much more than words," observes Nelsen. "It's much more effective to kindly, firmly, show them what they can do, rather than angrily lecture them about what they can't."
Fortunately, by between 18 and 36 months your child's vocabulary will jump from about 20 words to nearly 1,000, which means she'll be both better equipped to communicate verbally -- and less likely to act aggressively.