The baby sling has been used for centuries, and has recently gained great favor among modern mothers. It's felt that a small infant has more privacy with a sling (Actress Keri Russell says her sling is her baby's "paparazzi shield"!), and it's especially useful for nursing mothers.
There are several important things to consider when choosing a sling or front carrier. First, check the sling to see what size / weight it is rated for. Is the sling padded? Padding is excellent for protecting toddler's sensitive legs. When debating between baby carriers and baby slings, keep in mind that front carriers are designed for infants from 8 to 25 pounds, while baby slings can be used for preemies all the way up to toddlers at 35 pounds.
For soft carriers, make sure that it's washable and has adjustable straps. This allows you to keep the same great fit as your baby grows. Your baby should fit snugly, and have good head support, and their weight should be evenly distributed. Only use a carrier to move the baby about when you are walking. Never use it to transport the baby on a bike, in a car, or any other means of transportation. Check the carrier from time to time for any damage: things like a ripped seam, a missing or loose snap or strap, or a place where the fabric has worn through and a sharp edge is protruding.
Some car seats convert to lift-out-and-carry baby carriers. While these can be heavy and bulky, some mothers prefer them to traditional carriers. Many are designed to snap into a car seat base, or into a stroller. Only use those types of models together. Never take a base from one model (maybe that someone has given you) and try to rig up something to hold your carrier in it. In an accident, the carrier will break free, and your baby will become a projectile! If you own a new car, never put your baby's carrier / car seat in the front. In the event of an accident, the airbags could cause serious injury to your child.
In the case of a backpack carrier, consider getting one that can be worn on your back, side or front. It gives you more options depending on the age and temperament of your child. Some carriers provide a sun shield (which doubles as a rain guard) as an added bonus. Remember, the heat of the sun is much more damaging to an infant's head than an adult's. You want your baby's weight evenly distributed, so get a backpack carrier that's adjustable. Make sure the fabric is washable, and easy to remove; filthy cloth is a breeding ground for germs. Follow these tips, and your baby will stay safe and healthy and so will you.