How do I pick out the best car seat?

Google. Type in "best car seat". Into google and see the magic happen before your eyes. Swami google has all the answers.
Gather information. The best car seat is one you understand, that accomidates the length & weight of your child & can fit in your vehicle for a good installation every time. The $300 seat is not 3x better than the $100 seat. Web sites like nhtsa or safekids can help. Always keep the receipt after purchase and do a trial installation before you let baby ride.The trauma service @ my hospital sponcers a fittting service.