What exact positions would be optimal for target engagement, which target is fastest in the engagement order, where do you have to reload ect. Plan your shoot and shoot your plan. Work on visualizing the stage from start to finish. It has been proven that the mind cannot tell the difference between something effectively visualized and the real thing. Knowing exactly how your going to do something also has a calming effect.
Uncertainty is stressful.
When you step into the start box, relax your stomach muscles by taking a breath into the lower diaphragm. Run through the stage one more time in your head and then think of a key thought and focus on relaxing and waiting for the start tone. I use these and many more at different points in time and on different stages just depending on how I feel. S omething you may find interesting is to not treat any stage differently no matter where it is at. Always program a stage the same.