Mix sugar, milk and flavorings together until smooth.
I always end up adding more milk. If you do add more, be sure to add it a little at the time so your icing isn't too thin.
Add icing coloring to icing a little at the time until the desired color is reached.
Spread over cooled cookies right away since the icing sets up quickly.
You can stir in a bit more milk if it starts to harden too quickly.