Ready Styles
The Ready Style screen allows you to flag certain styles as "readied" you can also use this screen to unready styles.

A Readied style is a style that is used automatically in combat when you click the appropriate button.

It is wise to ready a few styles at different stamina requirements as during a fight your stamina will go down so you may not get the chance to cast your most powerful styles more than once.

By readying a good range of styles you will be able to execute a number of styles automatically without having to manually select them.