The next step is to see how the boot feels once it's laced up. From a seated position, gently tap your heel into the back of the boot and plant your foot flat on an even surface. Then, beginning at the toes, start to tighten up the laces. Pressure should be even and firm, but not restrictive. Remaining seated, follow the laces all the way up the boot, hooking onto any eyelets and finishing off with a secure bow.
This process gives you a good idea of the amount of space your foot is occupying inside the boot. If the boot is too small, the laces will be bulging outwards; too big and excessive tension will be required.