• The recommended placement for a car seat is in the middle of the rear seat, or the center seat in a van or station wagon, assuming LATCH attachments and/or a shoulder belt are available there. Never install a rear-facing car seat in a front seat equipped with a passenger-side air bag.
• Keep your baby in a rear-facing car seat until he reaches 12 months and 20 lbs. (10 kilograms) at a minimum – but the longer you can keep him in a rear-facing position, the safer he’ll be. Always check the manufacturer’s instructions for the rear-facing weight and height limits.
• If a baby under 1 year old grows too tall or too heavy for an infant car seat, a convertible seat with a higher rear-facing weight limit is recommended.
• Read the owner’s manual for your car to find out how to use your car’s seat belts or LATCH system with an infant car seat.
• Read the entire infant car seat manual.
  
  
• Use your knee to push down on the seat as you tighten the car’s seat belt or LATCH attachments belt through the car seat’s belt path. The car seat should not move more than 1 inch (3 centimeters) from side to side or forward and backward at the belt path. If the seat wiggles or moves on the belt path, the belt needs to be tighter.
• Some seat belts may require a special locking clip that is designed specifically to keep the belt from loosening.Locking clips are available from baby product stores, car seat manufacturers, and some car dealerships.
• Be sure to check the tightness of the car seat before each use.
  
  
• The car seat should recline at no more than a 45-degree angle.

Harnessing your infant

• Read the entire infant car seat manual.
  
  
• Your baby’s head should be at least 2 inches (6 centimeters) below the top of the car seat.
• Infant-only seats are usually designed with a 3-point or 5-point harness. The harness straps should always be placed in the slots at or below your baby’s shoulders. Most models have a chest clip that holds the harness straps together. Move the clip so the top of it is level with your baby’s armpits.
• All harness straps should fit snugly, especially over the shoulder and thigh areas. Straps should always lie flat, never twisted. If you can pinch any harness webbing between your fingers, it’s too loose.
• Dress your baby in clothes that keep her legs free. This will allow you to buckle the latch crotch strap properly between her legs. If it is cold outside, harness your baby first and then cover her with a blanket (never cover your baby’s head). Never buckle a blanket under or behind the baby.
• If your baby slouches to one side or the other in the seat (common among newborns), carefully place rolled-up cloth diapers or rolled hand towels on each side of his or her shoulders. There are supports specially designed for car seats, but only use them if they came manufactured with your car seat. Never place any kind of padding or blanket under your baby – this can affect the harness’s ability to restrain him.
• If your baby’s head flops forward (also common among newborns), check the angle of the seat. You can wedge a towel, blanket or other firm support under the front of the seat to tilt the seat back slightly (a 30- to 45-degree angle is best – never more than a 45-degree angle). Follow the manufacturer’s guidelines for the recommended angle of recline for the seat.

 
Go to nhtsa.gov for more information. And be sure to read the instruction manuals for both your vehicle and for the infant car seat before installation