Part of "practice smart" might be finding out what you need to know or need to be able to do, and then working at it regularly until you can. An example might be the ability to, without thinking about it, play a scale in any key. Another example can be found in the sentence above: "work at it regularly". Fifteen minutes a day is better than two hours once a week. Repetition is part of how the brain gets to know things, and knowing things is not the same as remembering things.