Men’s Thorlos mini crew socks
I have been selling Thorlos socks for the last sixteen years and have yet to find a better sock! The most important feature is they are made of a synthetic material - Thorlon - designed originally for diabetics - which wicks moisture away from the skin so your foot stays dry. This means that even if there is movement inside the shoe, there is no rubbing or friction on wet skin, which prevents blisters. (Cotton socks tend to absorb moisture and therefore the skin becomes wet.)
Furthermore, they are very, very comfortable and last for years!