A common question we get is what kind of socks should I bring - and what type of socks should I ski in? For trying new ski boots, we recommend you wear very thin socks - either ski socks or even dress socks. The reason is that new boots have not packed out yet, so you will get a better idea of how they will fit by going thin.
For actual skiing, it comes down to preference and fit. If your boots are very tight, thin socks may be better; if your boots are becoming a bit loose, a slightly thicker sock might improve the fit. While some people in the industry believe that thin socks are warmer, this is generally not true (might be true if a boot is extremely tight, otherwise not).
Other factors with socks are with materials and fit. I find wool socks like the Smartwool Ski Light to be comfortable and warm, but they need to be washed regularly and might be an issue when on vacation. Another option worth considering are compression socks, which most skiers find warmer than other ski socks. Be aware that they needed to be fitted to the size of your calf circumference. Speaking of calves, a number of clients with large calves have said the only comfortable socks they have been able to find have been snowboard socks.
One last option is heated socks, which have generally proved to work very well. More on this in the boot heater section.