There are a few key factors to consider when evaluating the quality of bed sheets:

Thread count: The thread count of a bed sheet refers to the number of threads per square inch of fabric. In general, higher thread counts are considered to be a sign of higher quality, as sheets with a higher thread count tend to be softer, smoother, and more durable. However, it's important to note that thread count isn't the only factor to consider, as other factors such as the type of fiber used and the way the fabric is woven can also affect the quality of the sheets.

Material: The material used to make the bed sheets can also impact their quality. Natural materials like cotton and linen are generally considered to be high quality, while synthetic materials like polyester may be less expensive but also lower quality.

Weave: The weave of a bed sheet refers to the way the threads are interwoven. Tightly woven sheets tend to be smoother and more durable, while loosely woven sheets may be less expensive but also lower quality.

Finish: The finish of a bed sheet refers to any treatments applied to the fabric to give it certain properties, such as wrinkle resistance or a softer feel. Some finishes may be applied using chemicals that can be harmful to the environment or to people with sensitive skin, so it's a good idea to choose sheets with finishes that are safe and eco-friendly.

Brand reputation: Reading reviews and researching the reputation of the brand can also be helpful in determining the quality of bed sheets. Brands with a long history of producing high-quality bedding products are more likely to continue this tradition with their bed sheets.