In my experience, the first step is to get the physical basics right (sleep, exercise, nutrition/hydration). This is already hard for most people, but can bring

In my experience, the first step is to get the physical basics right (sleep, exercise, nutrition/hydration). This is already hard for most people, but can bring you to 100% of your theoretical mental performance as the baseline. To go beyond that, a daily routine of 2x20min meditation is somewhat proven to increase your mental capabilities slowly over time. Also background Music (like Trance or game soundtracks) have some instant effect, I personally have great results with Endel.io - highly recommend!