u gotta remember its just a game. no matter what happens, e.g. u go 1 for 20, score 50 points, miss/make the gamewinner, will not change who u r. so u have to remember that u have nothing to lose and everything to gain, and u gotta be excited to play and have fun rather than be nervous. u cant let negative emotions take control, because they are just a misconception of what is reality.

ii think the most important part of not being nervous and preparing for a game is being aware of all this. as for my routine, i usually just chill out (or shoot around) until its close to the game, then i listen to rap and just spend some time by myself envisioning myself on the court, think postive, and eliminate distractions. the key is to be calm and focused: its a lot harder than it sounds obviously, but with the right experience and mindset it cna be done.