What kind of adjustments does it take for a student who is playing well outdoors to go to an indoor environment? It is much easier to go from playing outdoors to indoors versus transitioning from indoors to outdoors. Playing indoors is very controlled and pure. You can control the climate, there is no wind or sun, and wherever you hit the ball, it will go since there are no elements whatsoever to affect the ball.
About a week before my players are planning to go back to play an indoor tournament, I start to alter the way they train. We start working on taking the ball a bit earlier, court positioning, serve and volley options, slice backhands, body serves, transitioning to the net, return of serve, first ball after the serve and of course, the most important shot in tennis—the serve. The game and strategy changes when transitioning from outdoor play to indoor play and vice-versa.
The speed of the court the player is going to play on is important. This is going to be key in constructing a game plan as to how the player is going to construct points to give themselves the best possible chance to be most successful. Typically, indoor courts will be faster than outdoor courts, but that is not always the case. If this is the case, the player may need to shorten their backswings a bit as well. As a kick serve is a great play outdoors, if the court is speedy indoors, a slice or sliding serve would be a better play than a kick serve.
Using the court to your advantage is very important. What does this mean exactly? One needs to devise a plan that works for the given type of surface. If the indoor court is fast, you will most likely need to play pretty close to the baseline to take time away from your opponent. If the indoor court is not fast, you could play a game style similar to how you would play outdoors where you would have a chance to play more of a multidimensional game style. This could include playing a little further behind the baseline, play a bit more defense, and even add height to the ball if that works against your opponent.
Further, to understand how the particular player is going to play that particular indoor tournament, I usually have my students get to the tournament site at least two days in advance so they can get their timing down and devise a plan on how they are going to construct points. It takes a much longer time for one to become used to an outdoor court coming from an indoor environment, compared to coming from an outdoor environment and adjusting to an indoor environment. It all depends on the speed of the court to whether there are major or minor adjustments needed. What makes tennis such an intriguing sport is that there are so many variables that one must take into account to play at their best level week in and week out. Every tournament a junior tennis player plays in takes proper preparation so that they can play at their optimal level for that given event. Best of luck adapting!