Many techniques have been advocated to improve hammer control, but none, I think, are as effective as the following:

1. Get the biggest sledge you can reliably swing.
2. Buy 3 extra hickory handles--you will need them.
3. Purchase 8 steel wedges.  Yes, I said 8--you will need them too.
4. Acquire at least 1 cord of unsplit elm.
5. Spend at least two hours each day splitting, using only full swings (like half swings will do anything but make the log laugh.).

Wear safety goggles, there'll  be wedges a-flyin' everywhere.  As one wedge gets stuck, widen the fissure at some other point with a second.  I personally have had as many as seven wedges stuck in one knotty old stump.  If you finish the cord, you'll have dressed the wedges at least once, and be on that third handle, but your skills will be ample to perform brain surgery on a hummingbird in mid-flight with that hammer!  The particular advantage to this method is that each time you swing for your target (wedge) it is at a different height and angle, and unless it is struck dead center you waste the blow and the wedge goes airborne.  Heck, it isn't any challenge to hit an X on a piece of wood sitting there in the same place each time.  What a wood splitter learns is how to place the hammer exactly where he wants it, at exactly the angle he wants it, with exactly as much "pop" as he wants it, under the worst conditions possible.  Moving from here to an anvil is a picnic.
    Next time Frank tackles getting the holder and the striker together on where exactly the hammer is goin' in SLEDGE Team striking part VII "X Marks The Sweet Spot".  Till then watch out  for flyin' wedges!