Discover or define your personal playing style. This is extremely important to know because it will allow you to take a clear approach to matches. Are you in the category of a retriever (you don’t have tons of power to hit winners but your foot speed and defense let you get many balls back)?
Or are you an aggressive player (you’re not the most consistent but you can dictate points with your power)? Once you know your own style, start watching some professional tennis on TV or in person. This is not necessary but it can be a very helpful step. Look at where the pros hit and the tactics they use. Obviously you won’t be able to use the same plays to perfection but it can put some ideas in your head.