A couple of recent lessons have highlighted a critical component of practicing for me. I had a student work through an exercise, playing it mostly correct, except for one added note in the ride cymbal part. It was a very typical coordination error, as the snare was playing on that beat as well. I told the student there was one thing that wasn't accurate to what the written exercise clearly showed, but made it a point not to tell him what it was. I wanted him to be able to tell me, and he couldn't. He didn't know.
Another recent lesson had a student playing through a different coordination exercise. Same effect: he was playing something inaccurately according to what was written but didn't know what. In fact, just like the other student, he wasn't even aware anything was out of place. So I recorded him playing it and played it back for him so he could listen and count along. During the first time hearing what he'd played, he discovered something was off. After going through this process of playing/recording and listening a couple more times, he was able to quickly hone in on the problem spot (without my pointing it out) and correct it.
This is a problem I see with many--I'd say most--students I encounter, which is a lack of awareness in their personal practice. What concerns me isn't that they come in to their lesson playing something "wrong", per se; it's that they simply don't know that anything actually is wrong. This tells me they're not really listening to what they're doing with the level of attention that's needed. It's hard to correct errors if you're not aware of them. I often say, "You're accountable for every note you play. Know what you're playing at all times." Only through total awareness of the exercise at hand are you able to develop it. Otherwise, you're wasting a lot of time with mindless, inefficient practice.
Here are two ways to help build a higher level of awareness in your practicing:
1. Practice SLOWLY and deliberately. Slow practice is one of the main ingredients to solid development for many reasons, and one reason that applies here is the fact that practicing at a slow--often VERY slow--tempo allows you to be aware of more musical details than practicing at fast or even moderate tempos does. You're giving yourself more time to listen and think.
2. Record yourself. In the second example, the student had the opportunity to hear exactly what he had played just seconds before, while reading the written exercise and counting along. Being able to "step outside himself" and listen objectively allowed him to find out precisely what he had played inaccurately and quickly adjust.
If you practice with your full concentration, focus and awareness on the task at hand, your development will accelerate noticeably. You'll find you're accomplishing more--much more--in a shorter amount of time than before.
"The right kind of practice is not a matter of hours. Practice should represent the utmost concentration of brain. It is better to play with concentration for two hours than to practice eight without. I should say that four hours would be a good maximum practice time—I never ask more of my pupils—and that during each minute of the time the brain be as active as the fingers.”
-Leopold Auer, noted violinist, composer and instructor
Here is a link to a great article on practicing slowly. Notice the word "mindful" and when it comes up. Mindfulness is the same thing as awareness (likewise, mindlessness is lack of it).