I purchased the Britax ADVOCATE 70-G3
child seat. It is expensive but rich on safety features. Detail report on purchase and user review in this post
Compared to shops, I found much better prices and variety in online deals especially during clearance season. Some good brands are Graco, Chicco and Britax. Some advice for selecting car seat:
0. First read car seat requirements and recommendations from independent bodies like AAP
(American Academy of Pediatrics). Or these car-safety.org guidelines
1. Look at baby's age and plan well into future. Ideally, your car seat investment should last you till 5 years.
2. Before purchasing, visit manufacturer website and download online pdf manual to confirm what is the weight, length of baby that the car seat can support. Usually there are min and max for weight and baby length. If the car seat is convertible (rear+forward facing), then the ratings will be different based on what position it is in.
3. Confirm if your car seat belts are compatible with your car seat. Eg. some car seats are not compatible with motorized, automatic seat belts.
4. If you plan to change your car in near future, make sure your seat will be compatible with your future car too.
5. ISOFIX/LATCH is a new global standard for attaching child seat. This is supposed to be safer than conventional seat belt attachment. If your car supports the former, look for seats that support it.