I don’t know exactly how to prepare for this but I can share my opinion regarding this. If someone wants to start preparing for a future higher from now onwards while studying in lower or small classes they can definitely. There is no rocket science in this.
For doing this we should start focusing on the basic concepts of the subjects that we want to take in the future. Building a strong foundation helps in the near future always. For example, if you want to prepare for medical in the near future start focusing on Physics, Chemistry and Biology. Brush up your basic concepts because all things are ultimately based on the basics of the subject.
Start taking knowledge about colleges and institutes that you want to take admission for pursuing that degree and if there is any entrance for that. Start preparing for that also. If you start taking knowledge about all this your aim and the path to your aim will become clear and visible.
If there is anyone in your family belonging to that particular field, take knowledge from them about that field all the latest updates and trends.

    GeetYaduvanshi I would advise you not to do that..you do one thing with total dedication, it will yield to u in many different ways..changing ur choices often getting lured by other things will make u regret later. Just focus where you are.

      GeetYaduvanshi I think the question has come because you must be a meritorious student. You must be solving math problems of higher standards. If this is the scene, you must realize you are already preparing for that. If this is not the scenario, you must focus on whatever you are in, rather than eyeing on something else. It’ll destroy your present scope too. Best of luck.