kenny, I agree, sometimes no matter how you break the shell, there will be pieces that fall into the egg.
I don't often have it happen, usually does when I'm in a hurry -
and maybe that is the reason.
I prefer using a sharp edge to break the shell, either a knife with egg in hand, or on the edge of pan, etc. I truly prefer this to a flat surface. Reason is a flat surface creates a circular pattern of shattered shell. An edge has more of a tendency to create a line crack, sometimes even two taps.
But it is with practice you get the right amount of pressure with your whack.
With the line crack the shell is easier to split in half around the equator so to speak.
A circular crack means you have to apply more pressure to open the shell and you don't always get an even break around. This creates more cracks in the shell and more chance of a loose piece falling in.
All this is just my HO.
Another thought is just how many whacks are you giving your shell to open? One is generally enough, two on occasion. Three, I should think, you are starting to pulverize the shell too much.
My last suggestion is - always crack your egg into a separate container. You can then fish out the shell if necessary. Much easier to do than watch it in a hot pan or slide down the flour and butter in the bowl.