Sockets have many things in common with wrenches. They same ideas of fit apply, and the same ideas of 6 point and 12 point apply. Sockets also have depth, so you need to consider sockets that are normal depth, shallow (to fit into tight working areas) or deep, to help you reach hidden places like spark plug holes. It is customary when buying sockets to purchase 4 major sets. Normal Metric 6 point, normal Metric 12 point, normal SAE 6 point, and normal SAE 12 point. These sockets will be used for practically every DIY job on your truck and you should purchase quality tools here. You may also find that you wish to purchase flexible extensions to allow you to work at awkward angles. These are just a few dollars but are often worth their weight in gold when working in tight areas.
Sockets come in a variety of "drive sizes" usually referred to in the US as 1/4" drive, 3/8" drive, and 1/2" drive. The 3/8" drive is the most commonly used but the 1/2" drive sizes will be of great use as well on our trucks because many of the fasteners underneath use quite large fasteners and require more torque be applied than can safely be done with a 3/8" ratchet.