Make sure the CRS is compatible with anchorage systems (2 or 3-point seat belt), ISOFIX or LATCH, and that it fits (effortlessly) in the car. Installation of anchorage systems that are not originally included in the vehicle or in the CRS is not recommended. If possible, it should be tested inside the vehicle before purchase.
Given that the majority of CRS available in the market can be installed with 3-point seat belts, in case that your vehicle only counts with 2-point belts, consult your official dealership to check if there is any possibility of replacing them for 3-point ones. Do not accept changing them for generic belts or imitations, only for original brand ones complying with technical standards.
Verify that the CRS complies with the internationally recognized standards.
Verify the CRS´ expiration date. In general this information is in the outer layer of the child seat and/or in its manual.