Walk-Back" method – center-shot
Using your fletched arrows only and from 20 meters (or yards), shoot one arrow into the paper. Now, WITHOUT MOVING YOUR SIGHT, move back to 25 meters, aim at that paper and shoot another arrow. Keep going back in 5 meter increments firing one arrow at each distance WITHOUT MOVING YOUR SIGHT. How far you can go back (because the arrows will be hitting lower and lower) will be limited by the size of the butt and your arrow speed but most will be able to get back to about 45-50 meters and have 6-7 arrows in the butt. The object of this method is to obtain a vertical line of arrows from top to bottom - if you're lucky enough for that to happen then don't make any adjustments to your center-shot. On the other hand, you may end up with your 6-7 arrows forming several distinct patterns. They are:
(1) ARROWS TRACK LEFT AS YOU GO FROM TOP TO BOTTOM. If this is the case, move center-shot to right in small increments.
(2) ARROWS TRACK RIGHT AS YOU GO FROM TOP TO BOTTOM. Move center-shot to the left in small increments.
(3) ARROWS FORM A SEMI-CIRCLE OR CURVE FROM TOP TO BOTTOM WITH THE BELLY OF THE SEMI-CIRCLE/CURVE ON THE LEFT. Increase poundage in small increments.
(4) ARROWS FORM A SEMI-CIRCLE OR CURVE FROM TOP TO BOTTOM WITH THE BELLY OF THE SEMI-CIRCLE/CURVE ON THE RIGHT. Decrease poundage in small increments.
I will also mention with regard to the above patterns that there is another school of thinking which suggests that the tracking pattern described in (1) & (2) is related to poundage (not center-shot) AND that the curving pattern described in (3) & (4) is related to center-shot (not poundage). In other words, that school of thinking would apply the solutions from (3) & (4) to Patterns (1) & (2) and the solutions from (1) & (2) to Patterns (3) & (4). My suggestion is to keep an open mind and try each solution (or a combination of both) and see which works best for your set-up. Remember, the object of the method is to obtain a vertical line of arrows from top to bottom.
On a final note, take time with your testing and re-check your results until you are satisfied that you have obtained the best possible tune you can with the above methods. If you have done everything properly, you should have very little further adjustments (if any) to make when you do your "group tuning".