Constraining one's 'acceptable hits' area on a target does wonders for one's concentration. (And by 'one' I mean 'yours truly.' YMMV and all that.)
ToddG of pistol-training.com loves shooting 3x5 cards and 8" paper plates (or equivalents). When shooting a 3x5 card as part of a drill, only 100% hits are acceptable. These represent precision shooting. On the plates, 90% hits are acceptable, as long as you are pushing yourself outside your comfort zone with speed. The FAST drill is both shurikens and lightning* and a good illustration of this philosophy.
What's crazy is that it goes both ways. Once one commits to getting 100% hits in a 3x5 card at distance X, one is more likely to get 100% hits in 3x5 card at distance X, while merely 'shooting a group' at distance X results in a 6" shotgun pattern. In my experience, at least. Similarly, I find that 'shooting the black' results in shots that all make their way into the black, but not a small group in the middle that should be more representative of a skill level I've demonstrated at said distance.
As a bonus, 3x5 cards and scotch tape are cheap. Plus, you can stick those 1" paster circles from Shoot-N-See packs (I never seem to use 'em otherwise) in the middle as a handy aim point. Thus configured, it looks an awful lot like The Black Spot, and what with shooting pirates *finally* being in vogue, that's pretty ninja.
* Adj. 1. Worthy of kudos; awesome. Origin: Zero Punctuation.