Serve Stance
When you become a consistent server, by being comfortable with your grip, able to hit different serves; flat, top spin and slice and then show good skills at placement, THEN I want you to stand in different areas of the baseline.
With your normal serves, you will add ‘more’ serves by only changing where you stand. The opponent will have trouble with different angles the serve will be coming from, just due to you moving from one spot to another.