How can you tell if fish oil is high quality?

How do you determine if fish oil is of high quality? Are there specific factors that you should consider when making a purchase, such as the source of the fish, the manufacturing process, or the presence of contaminants? Is it important to look for a third-party certification or label that verifies the quality of the fish oil? Can you provide some tips for consumers to help them make an informed decision when selecting a high-quality fish oil supplement?