Evaluate the features: Where does your dog like to ride? Front Seat, Rear Seat, Cargo Area... Ensure you are getting the cover that will work best for you.
If you are looking at rear seat cover, does it have a hammock feature. This helps to keep your dog in the back seat and often makes them feel more secure since they won't hit the floorboard every time you hit the breaks.
Does the cover have seatbelt openings that allow you to attach a harness to secure you pup? Do the openings Velcro closed to keep dirt and fur from getting behind the cover?
Is the cover waterproof? How easy is it to clean? Is it made of a durable fabric?
What features does it have to keep the cover in place? Does it have a nonslip backing? Seat Anchors? Does it have clips which allow it to be installed or taken out quickly?
Is it covered by a warranty? How long does the warranty last?
Evaluate the workmanship of the cover.
What type of material is used? Is the material free of heavy metals and harmful dyes? What is the weight of the material/ how durable is it? You want a material with greater than180 GSM heavy duty material.
Finally, evaluate the company you are purchasing from.
Always check out their reviews. If many of their reviews have a disclaimer stating they are reviewing this product in return for receiving it at a significant discount, it may be hard to trust those reviews. How long has the business been around? Do they have their own website? Do they offer other products? This helps to evaluate if the company is going to be around long enough to stand behind their warranty.