What you'll be looking for when you go to buy a car seat will depend on several factors, including the age of your child and the type of vehicle you drive. There is no 'best' car seat; the best seat is one that is suitable for both the weight and size of your child. All current car seats on the market pass necessary safety standards. Select the one that best fits your child and your vehicle. Some models have different features; choose the one that helps you use it correctly every trip and don't be tempted to assume that a higher price means a higher level of safety.
Make sure that the harness fits your child snugly, that the car seat is well fitted and that your vehicle seatbelts are in good condition. If you can't try the car seat out before buying it, then make sure there is some sort of return policy. If the seat doesn't fit your child or vehicle, or you decide it's just not the right seat for your child, you'll want to be able to return it for a refund or store credit.
It is tempting to purchase second hand car seats. If you are considering a second-hand model, pay particular attention to the age of the seat. Try to avoid car seats over six years old or those which may have been in a crash, and look carefully for cracks or signs of wear on the seat and restraints. Whether you're purchasing something new or second-hand, pay attention to recall notices. For more information regarding child car seat recalls, check out the U.S. Consumer Product Safety Commission Web site or the NHTSA Web site.
When looking for car seats you may see references to LATCH. This is a new system developed to make car seats easier to use safely. LATCH stands for "Lower Anchors and Tethers for Children" and eliminates the need to use seat belts to secure the child car seat to the vehicle. However, your vehicle must be fitted with the anchor system. Starting in the year 2002, most new vehicles began to be manufactured with the LATCH system installed. LATCH is not necessarily safer than using seat belts to secure a car seat, though it may make it easier to achieve a safe installation. Your child car seat retailer will be able to advise you on suitability for your vehicle. Many of today's child car seats can be used with both the LATCH system and regular seatbelts. So if you have two cars, one with the LATCH system and one without, but only have one car seat, you'll want to find a seat that works with both restraint mechanisms.