Teaches:
accuracy, proper follow-through

Requires:
range, optional rentals-availible shooting range, small reactive targets

Drill:
Try these out and keep the ones you like.

• Dry fire a LOT.
• If you can see the muzzle flash, (1) you aren't blinking and (2) your eye was properly focused on the front sight. If you don't see the flash, check to see what your eye is doing.
• Watch your sight and note that it goes straight up and straight back down as if on a spring. If the sights do anything else (e.g., pause at the top of the recoil arc, move sideways, "bounce" around at the bottom of the arc), then you are applying excess muscle force somewhere. You can't suppress recoil 100%, but you can manage it by riding with it. Think symmetry.
• Make sure that for consecutive shots you are not shifting your grip or slapping the trigger.
• Shoot at small reactive targets, like spinners, at a difficult distance.
• Wear good hearing protection.
• At a rental range, fire a heavier caliber than you usually shoot; then go to your lighter gun.
• Fire at a longer distance than you usually do for a while; then bring your target in closer.
• Fire at a longer distance than you usually do for a while; then bring your target in closer.
• You'll have a greater field of view if you shoot with both eyes open. For competition, if you find it difficult to do so, try putting a strip of transparent tape on your shooting glasses over your non-dominant eye. It will enable the strong eye to focus while still retaining some depth perception and peripheral vision.
• Don't visualize yourself shooting at the target; visualize yourself shooting into it.
• Intersperse your timed/stress shooting (starting from low ready, or a holster, shooting at multiple targets, reloading, etc) with precision shooting as well. Brian Enos recommends starting and ending every shooting session with precision shots just to remind yourself that you can do it, and to have a feeling of balance and accuracy going into the more speed-oriented shooting.
• If you have trouble figuring out adjustable sights, imagine that the front sight is a foot tall. Now imagine how the gun barrel tilts. For windage, imagine that the rear sight is a foot off to the left or right. This simple visual exercise will help you see how the sights work.
• Read the US Army Marksmanship Unit's Pistol Marksmanship Guide (for competition bullseye shooting).

Credits to Julius Chang, and several rec.gun posters whose suggestions I have remembered, but whose names I unfortunately haven't.