Spin Stop

While standing in one place, lift the heel of your right skate. This exercise is a
key component in the spin stop. It gets you familiar with the necessary movement
while you are standing still.
While standing in one place, practice your heel rotation, pivoting off the first wheel of your right skate for a clockwise rotation & off the first wheel of your left skate for a counterclockwise rotation.

Avoid over-rotating by not going into your A-frame turn too fast.

If you are off balance, check your hand position. They should be in front of you at waist level throughout the turn. To get the tight turning arc you need for best maneuverability & control, lean forward with bent knees as you enter your turn and apply pressure to the inside edges of your skates.
The skates are scissored and the trailing skate is pivoted on the toe wheel so that the
toes are pointing apart & heels together, but not touching. Weight is transferred to the inside wheel edges to enter the spin. The wheels actually scribe an arc. This is usually done at slower speeds.
Source: mysportsguru.com