For this hammer hack, you can make adjustments based on your home repair expertise (and experience). If you often miss hitting nails by a mile, opt for a larger DIY shield. And if you tend to hit your fingers when hammering nails, you can drill a little notch next to your nail hole in the shield and use it to hold up the nail when starting it.
As for the hole in your shield, where it’s placed will determine where you can drive nails with its protection. Centering your nail hole along one side, near the edge, will give you a lot of flexibility to use your shield near walls, protruding spacers, etc. Meanwhile, you’ll get maximum benefit from drilling your hole near a corner of the shield; however, keep in mind that the closer to the edge of the shield you need to strike, the less protection it will give you from potential dings.