From my personal shooting, in which I am ever practicing to perfect....is to take several deep breaths..rest and relax your mind. Focus on the target/dot and clear your mind of all but achieving your objective. Focus on the target not the crosshairs, Take your time, and concentrate. Think of where you are putting you check on the stock, where you hold everything, does it feel the same as the last time you fired your last round? If not then realign to make it. Then I take a very deep breath, and hold for a split second, and exhale all the air left in my lungs ..and relax and hold...this is my opportune time. My heart rate and time is all slowed down. This time doesn't last long. If you hold your breath to long your heart will start to beat harder. At least mine does. And then I have waited to long.
Perhaps this isn't the absolute best advice from a world class champion target shooter, but it puts me in the frame of mind I need to be.