Quality of the fabric: You want a T-shirt that is made from a quality fabric that won't shrink, fade, or pill after multiple washes.
Fit: Make sure you get the right size for your body type so that the T-shirt fits properly and is comfortable.
Style: Depending on the occasion, you may want to choose a T-shirt with a specific style or cut.
Color: Consider colors that will look good on you and go with your wardrobe.
Price: Make sure you get the best value for your money.