Modern skates provide firm support around the ankles. To accomplish this, the skate manufacturer installs stiff leather inserts between the outer and inner layers of the boot. Old skates may lack this stiffness; in used skates, it may be broken down from use or abuse.  Please see a list below of things to watch out for when buying skates:
With the skates laced up snugly, the ankles should be straight so that the skate becomes a natural extension of the leg. If the skater's ankles lean inward or outward, the skater will have difficulty balancing (particularly on one foot).
Molded plastic skates are not a good choice. They provide a lot of support but they cannot be 'broken in'. This prevents the boot from flexing properly to allow the skater the required range of motion.  The plastic skates with buckles instead of laces may be convenient but they often come loose leaving the skater with no support whatsoever.
Skates should fit more snugly than regular shoes, particularly around the heel. A properly fitting skate should have no more than 1/2 inch of space at the toe. The skater should be able to wiggle toes inside the boot, but the heel should not move at all in the skate. The ball of the foot should come just ahead of the point where the sole starts to cut in for the arch. This ensures the proper positioning of the arch and is extremely important.  The front opening of the boot should be sufficiently wide to pull the laces tight. The tongue should be sufficiently wide so that it will stay in place; the tongue should also be well padded to prevent laces from cutting into the foot.
Skates that are too small will be very uncomfortable for skaters and their feet will tend to get cold very quickly in too-small skates. Skates that are too big do not provide sufficient ankle support and may even cause blisters due to rubbing inside the boot.
Skates should be worn with one pair of thin socks. Thick or extra socks may appear to fill up the space in a skate that is too big. However, as soon as the skater tries to exert pressure against the boot, the extra thickness compresses and the skate doesn't provide the needed support. Never buy skates that are too big so they will last another season.
Skates should be laced fairly loosely over the toe and front of the foot, but snugly over the ankles. Laces should be hooked securely with sufficient tension to permit one finger down the back of the boot. Laces should be long enough to be tied in a double bow and tucked in. Laces should never be wrapped around the top of the skate.
A new pair of skates must be sharpened before they are used. An unsharpened skate has a flat surface on the bottom of the blade. It will easily slide sideways when the skater tries to push. The sharpening stone grinds a concave contour which produces the two 'edges' that dig into the ice.