Tiny Tooth Care
As soon as the first tooth comes in, don't let your baby fall asleep with a bottle of formula, milk, or juice, or, if you're breastfeeding, while he's nursing: The sugars will pool in his mouth and set the stage for cavities.
One of the best ways to ease sore gums: Massage the spot with a clean finger.
For an in-a-pinch teether, stick a clean damp washcloth in the freezer until it's icy cold (not frozen), then let your baby gnaw away.
Skip the zwieback, the frozen bagels and bananas, and other old-fashioned forms of teething relief: These foods can break apart in your baby's mouth and become choking hazards.
Likewise, don't rub brandy or other kinds of alcohol on your child's gums. If he's really hurting, give him an age-appropriate dose of acetaminophen (or ibuprofen, if he's over 6 months).
Note that your baby may not sprout molars until well after his other teeth are in, so the last thing you'd suspect if he gets cranky is that he's teething. If you discover that those back teeth are indeed making an appearance, offer him something to gnaw on and/or giving him a pain killer.

Essentials for Teething

As much as you love your baby's toothless grin, you're going to go nuts when his first tooth pops in--anywhere between 4 and 8 months. It will most likely be one of his two bottom front teeth. (While there can be all sorts of variations, most babies get their teeth two at a time, in this order: lower central incisors; upper central incisors; lower and upper lateral incisors; first molars; canines; second molars.) While your baby's dental debut is going on), it'll help to have a few things on hand to a) help him feel better if it hurts; and b) start taking care of those precious pearly whites.

Choose a teething a ring or toy that your baby can bite against, but that isn't too firm. Gel-filled ones are great, because you can stick 'em in the fridge: The cold plus the pressure of biting down is especially soothing to sore gums. (A note of caution: Don't put teethers in the freezer: A rock-hard hunk of plastic will be more hurtful than helpful to sore gums.)
You can rub one of these liquids or gels directly on the part of the gum where a tooth is about to break through (it may look a little red and swollen). Be sure to buy a product that's made for babies--not an adult formulation.
No, you don't have to set a timer and spend two solid minutes scrubbing away at your baby's handful of teeth twice a day. But you should get into the habit of brushing what he's got as soon as they start to come in--in large part to get him used to it. Brush-wise, you've got a few choices: You can go with a silicone or rubber gadget that's curved to fit around each tooth; or you can simply buy a baby toothbrush. It will say on the package that it's for infants--and should have a small enough head to fit in your child's mouth comfortably, super soft bristles, and a handle that you can get a grip on.
It's not really necessary, but toothpaste made just for babies usually tastes pretty yummy to them, and might make your little one more cooperative. Be sure to only use a toothpaste that has no fluoride: It'll be a few years before your child can rinse and spit, and swallowing a lot of fluoride can be harmful.
One more thing: If your child is absolutely miserable when a tooth is coming in, do all you can to help him feel better--and that includes piling on the hugs and cuddles. He'll feel better--and you'll enjoy some sweet moments with your baby to boot.