The socks that you wear to try the shoes on will make a difference. To get the right fit, you are going to want to wear the same type of socks that you plan to regularly wear with the shoes. As you may know, different socks that are made from different materials may have varying degrees of cushioning and thickness and this can alter the way that a shoe will fit.
If you are going to buy a pair of running shoes, then bring the type of socks that you plan to run in. If you are buying shoes for work, then bring the same type of socks that you wear to work. If you are looking for snow boots and you know that you plan to wear more than one pair of socks, then you should wear more than one pair when you try them on.
In addition to this, you want to make sure to use the little disposable socks that they have at the shoe store. It isn’t a huge risk, but other people may have tried those shoes on before you and it could expose you to different types of bacteria that can result in something like athlete’s foot. The protective socks are very thin; they will not make much of a difference when it comes to fitting.