Stay focused, blank out all possible interference
As part of my pre-shot routine I always pick out some point just ahead of the ball on my line to the target, and then focus on aiming at that. I have found that doing this helps me to blank out external interference (crowd noise) and helps me to zero in on what I’m trying to do. Starting behind the ball, I draw back an imaginary line from the target back to the ball, and pick out a spot just in front of the ball which I refer to the whole time, making my grip as I circle in to the ball.