TargetTalk

I have been told to use a slight degree of tension in my standing position. Does anyone know how much?? I know muscle activity is supposed to be present in my trigger hand; should tension be present in any other part of my body?? I have been shooting for years, but I cannot seem to get a good answer to this question!

It's imposible not to have a slight amount of tension in any position, including standing. The key is to manage it and use whatever is there to your advantage. I was always told that tension of about 10% in the quad and feet muscles is about right. This works for me. The key is to be comfortable and use just enough to maintain your balance while holding the sights on target. There should be relatively no tension in the upper body except to hold your right arm up to the grip and just enough in your back to stand upright. I personally have to pay close attention to relaxing my right shoulder (i'm a righty).
You may have to adjust the amount of weight on your gun or adjust your position slightly to improve your balance. Most of the shooters Ive seen with tension problems have them because the gun isn't centered well over the body while in the "back bend/body twist" position.
Patient experimentation is the way to go. A great way to do it is by doing holding exercises and dry firing.