The factory says it is fine to dry-fire your GLOCK.  Some accounts suggest otherwise.  Right off the bat, I’ll tell you that I dry fire the hell out of my Glocks and have never had a problem.  I don’t use snap caps or any gizmos or gimmicks to reduce the striker slamming into the back of the breech face.  Glock may be changing its tune, though.

This is a touchy subject.  It brings into question all that is ‘perfect’ in the Glock world.  Over the years I’ve seen breech face failures that appear to be in part due to dry firing.  Occasionally, a circular crack, the size of the brass cartridge rim, forms on the breech face around the firing pin hole.  This section then pushes out when the operator is dry firing.
Here are my observations:  The crack is precipitated by normal firing of the weapon.  This is obvious.  The plug of metal is the size of the cartridge, not of the shoulder of the striker.  The forward movement is due to the hammering firing pin on the already loose section.  Glock will always fix this problem.  I believe it is a manufacturing issue in certain guns, not operator misuse or abuse.  No failures, catastrophic or otherwise have been ascribed to this problem, but who knows. 
Snap caps are suggested as a remedy, but this may not prevent the cracking, only the forward movement.  Personally, I’d like to know if my breechface is cracking, so I continue to dry fire without snap caps. 
If you choose to use snap caps, you needn’t rack the slide completely and eject the dummy round with each trigger pull.  Simply rack the slide enough to reset the trigger.  Like a press check.  This saves you from chasing rounds around the room.
Remember, if you use dummy rounds, do not have live rounds in the same vicinity.  Load a snap cap into the magazine and rack it into the chamber.  Do not drop it in from the top.
Another way to exercise your trigger finger is to jam the slide open a little with a piece of paper so the trigger does not engage.  This allows the trigger to move back and forth without setting.  You do not get the click, but, like I said, you can exercise your finger. 
Recently, GLOCK’s official stance on dry-firing has changed.  The factory now encourages the use of snap-caps if more than the necessary number of dry-firings is performed.  Is this due to new designs or manufacturing processes of the Gen 4 pistols?  Is it an attempt to blame manufacturing inadequacies on owners?  I don’t know.
Are Glocks perfect?  No, snowflakes are perfect.  Glocks are machines that are man made and operate within certain perameters.  Glocks are awesome, not supernatural.
Be safe and keep on Glockin’