You want your child to be as safe as possible when you travel - all parents do. But when installing a car seat, whether it's for an infant, toddler or bigger kid, many parents make some common mistakes that could cost the child his life. First, start by choosing the safest car seat in your budget. A garage-sale car seat may seem like a steal, but it may not protect your precious cargo. The same goes for that hand-me-down from your sister. A secondhand seat is likely not to have the owner's manual, which is vital for installation, and the plastic with which it's made could be old and brittle - making it less sturdy in an accident. Car seats actually have expiration dates stamped on them. Check it if you must use someone else's seat, and be sure it is not on the U.S. Department of Transportation's recall list. Moving children up to the next level of car seat too soon is another mistake parents make. Children should be 20 pounds and at least one year old before they may face forward in the seat, and they should weigh at least 40 pounds and be at least three years old before moving up to a booster.