"While you can't reason with an infant or make him understand consequences, you can lay the groundwork for better behavior by using calm, consistent responses," says Karen Breach, M.D., a pediatrician in Charlotte, NC.
A few no-no's, and what to do:
Biting while breastfeeding
Tempting as it is for a teething baby to try out his new choppers, let him know right away that this behavior's not allowed. Either draw his face into your breast (he'll have to let go to take a breath) or insert your finger between his mouth and your nipple to break the seal. Firmly say "No" and put him down, and he'll learn that biting means the feeding is interrupted.
Tossing Cheerios from the high-chair tray is as fun as it gets: The snack gets some air, Mom grimaces, and the dog rushes in to lick it up. Pitching peas, however, is a sure sign that your baby isn't hungry anymore. Simply give him a stern look, say "No throwing," and take him out of his seat. You'll teach him that you're not amused when he litters the floor with food.
Hitting, poking, swatting
All babies experiment with how hard they can whack something, clap their hands, or bang blocks. If yours takes a swipe at you or Fido, demonstrate how to pat softly. Put his hand to your cheek as you say "Nice mommy," and he'll see that a tender touch earns smiles and praise.