Aswell as being a martial artist, I teach music privately. Learning technique for music and for martial arts is not entirely different (you may be surprised to discover). It involves learning and reinforcing a precise movement of series of motions so that they become easy and effortless.
In music, I always recommend investigative practice. That is, practice at the keyboard that involves, quite literally, investigating movement - how does each joint move, feel, where does the weight go, which muscles bear the load, etc. This is equally applicable for martial arts. Stand infront of a mirror and observe yourself. How does it look? Is you body in the right kind of alignment... are you using the right kinds of muscles? A karate style kick will often use local muscles to create snap, while a muay thai style kick may involve a more global effort, etc.
Watch video footage, or even better, have another demonstrate for you. Try to figure out the movements involved and how it feels to perform them yourself.
Ultimately, it involves using your brain, being analytical, etc. This how a dancer practices infront of the mirror for hours, making sure every line is perfect - this is how we have to practice technique also.
Also, think about the criteria you want to apply - what defines 'good' technique? In martial arts, the technique has to be effective and efficient before looking good. It's good to keep this in mind as often more aesthetically pleasing motions are less useful in actually combat.
alleycat