Most people think when shopping for ski equipment that the actual ski's are the most important piece, but the truth is it is the boot.
Finding the right pair of ski boots to fit your feet properly can be a challenging experience. Learning about different brands and reading their reviews is a great start but the only way to find the proper fit is to actually try the different brands on.
Ski boots are supposed to fit snugly, in fact most professional ski shops will have you trying on one whole size smaller than your shoe size. When trying on boots you should know that your toe should touch the front of the boot when you are standing in an upright position. As you fall into the bent knee ski position your heel and foot will automatically shift to the back of the boot pulling your toes away from the front.
Although snug, a ski boot should never be so tight that you can't wiggle your toes. You want to make sure that you are not cutting off circulation as this will help to keep your toes warm.
It is also important to only have on one pair of socks, the thinner the better. Thicker socks can actually make the ski boot feel smaller and crunch your toes, cutting off circulation.
If you are worried about your feet being cold there are a wide selection of ski boots that come with heaters installed, though if your boots are fit properly cold feet most likely will not be a problem.