There's an old saying, "The proof is in the pudding." This basically means you can taste or see the results immediately. I recently read a book by UofL coach Rick Pitino where he discussed in a chapter how long it usually takes him to see how hard a player worked in the off season to improve their game. Pitino said he could tell immediately within the first individual workout of the pre season if a player had truly put in the work during the summer to improve. Results are the proof and it is always plain to see.
WHAT TO DO? My advice to any player looking or searching for ways to improve an area of their game is to examine a proven-successful player who performs that skill at a high level. For example, if you're wanting to become a much better ball handler then examine a great point guard like Chris Paul. The proof is certainly in the pudding when watching Chris Paul handle the rock. Just watch him in pick & roll situations, in one on one isolation, or driving through traffic. He is a wizard with the ball and extremely gifted in changing speeds and directions with the ball. Now research everything you can on what he does in his workouts in articles, interviews and on youtube.
PROOF... In my own career I did this when my college coach came to me after my soph. season and told me he wanted to switch me from the starting shooting guard to the starting point guard for my jr. season. I decided that off season that I wanted to zero in and focus on becoming the best ball handler I could possibly be. I began doing a lot of research on youtube and other outlets and discovered the NBA skills trainer Ganon Baker. The first youtube video I ever saw of him handling the rock I knew that I needed to learn everything I could from him to take my game to another level. That summer I worked on my ball handling like never before and when our season rolled around the results where plain to see. I became an All-American and was asked by many people how I improved my ball handling. The proof is in the pudding.