What is precision?
There's a misconception about what it means to be precise, so to illustrate, let's examine two options:
OPT1: A direct punch going straight out.
OPT2: A punch that follows the target.
If we attempt to strike a given moving target, it is the natural inclination to want to follow the target (OPT2) as we strike. This extends the length of the strike beyond optimal, and decelerates into the target. Therefore, simply hitting the target is useless – we may hit the point we wish by following, but the strike becomes ineffective.
If we take OPT1, we have to assume there is a likelihood of missing our target, as we are punching where we are aiming, and our target can move. This is because we have a tendency (largely early in training when we're removing bad habits) to train commitment to the punch going to our target with full commitment, despite the fact it may move.
Precision is the culmination; the ability to connect with our target by striking straight and true. Therefore, we have to understand precision is the ability to strike a moving target with optimum impact.
Training for Precision
Training for precision is a progression. A precise strike moves straight out from the body toward a target first with maximum impact.
The Straight Strike
At the lowest level, we practice striking using the whole body. For this purpose, the heavy bag is extremely useful, and the shuddering of the bag without swaying lets us know the force is being kept inside the bag. In this way we train to throw hard strikes.
We need to also train to throw to where we're aiming, and we do this by punching past the target, albeit minimally. Our target, then, in this stage of training will not be a point on the body of our target, real or imagined, but a point in space in relation to us that is 1-2 inches past the current placement of the point we'd like to strike. In doing this we are training commitment: the strike going to a point in space, not on the opponent. When this becomes natural, we apply this targeting to a point in space where the opponent will be; either by his will or ours.
Small, Moving Targets
Sadly, the heavy bag is a stationary target, and there comes a point where we have to target something that's moving. A buyu of mine taught me a drill that I use to keep my reflexes sharp, and I practice it as an eye strike (like a punch, but the fore- and middle-fingers flick out at extension). Take a small square of black electrical tape and put it on a light drape over a window at about eye height, and toward the edge of the curtain. Let the curtain blow in the breeze and time your strikes to hit where the tape is going to be. You're still practicing a straight strike here, and you need to learn to anticipate an opponents movements. The nice part about training like this is that you're aiming for a very small point, and if you were punching, the motion is otherwise the same.
Tying it Together
Of course, at some point we have to bring it all in together, and the best practice is against a live target. Unfortunately, training against an opponent usually means that you've got to smack the bejesus out of them, and partners don't usually enjoy getting hurt. For this purpose, I recommend training armor. Whether you use something like Century's line of "martial armor" or "sparring gear", or any other line, the point here is to get you used to the less predictable (but still very predictable) nature of human movement, and striking with good intent and force to your targets.
Suggested Drills Against Live Opponents
1.) Have the opponent or a third party call out points to strike. Opponent moves but does not counter or block.
2.) Mark small targets on the opponent's armor using masking tape. Quickly strike what is available at a given time. Opponent moves and blocks but does not counter.
3.) Mark small targets on the opponent's armor using masking tape. Opponent moves, blocks, and counters.
4.) Mark small targets on the opponent's armor using masking tape. Opponent is openly aggressive.
Remember that we're trying to progress to build confidence in capability. Throwing a new student into the deep end and watching them get pummeled is not the right choice here, it's just setting them up for failure. I view drill 4 above as advanced training; it's full out live sparring with the added stress of training to strike specific targets; students need to be able to achieve a sense of mushin for this level of training.