Very, very good advice, Derek.
The only things I would add - You can either include the sling in your weak hand grip, or not. However, it must remain a tight "parade" sling in the off-hand position.
To shift your NPOA left or right, simply move the toes left or right on your rear foot. You don't need to shift your entire foot. Also, once you get your NPOA do not move your feet until you have finished your string of fire. If you move your feet, you have to rebuild the position from the start.
You should check your NPOA, as Derek described, and break the shot during your natural respirtory pause. That is, at the end of the exhale, 7 - 10 seconds max. DO NOT tilt / cant the rifle, DO NOT tense any muscles.
Follow through is very important also. After the shot breaks do not move anything until the front post settles back on your target. Don't take a breath, don't move the rifle, don't reset the trigger. This will help ensure you squeeze the trigger instead of jerking it, that you don't move the rifle before the bullet leaves the barrel, helps you stay relaxed through the entire shot, and, if your front sight post does not settle back exactly on the center of the target, your NPOA is not correct and needs to be adjusted.
Use the same routine each and every time, even during dry fire. During a match is no time to try new things.