Debussy Symbolism,
When you are talking about the "wrong way" to practice, are you referring to the hand motions etc. or the method of practice. For hand mechanincs I try to imitate pianists I have watched and try to incorporate the motions that I have read from C. C. Chang's book. Other than that, I videotape myself. Would it be nice if I have video taped a performance and put it here for people to comment?
Whilst there isn't a definitive "correct" way to practice, there are methods that secure a better technique. One of the things is the wrist positions. Playing with wrists raised will cause your fingers to be passive and a horrid sound quality. It's literally impossible to play with wrists raised. Concerning practicing scales, a good sound and good finger activity is important. I practice scales many ways, such as alternating fingers in succession, or holding down one note and playing the next one and so on. (Hard to explain). Raising fingers high whilst practicing scales in slow motion is important, as it gives a finger a good strenght and dexterity. In fast tempo you won't have to raise the fingers, but they will retain the dexterity. If playing scales with lazy fingers, then in "fast" tempo the notes will sound slurred. Relying on the videos of pianists play isn't as reliable in my opinion, because they already have the technique down, and so how they really practice isn't really shown in their playing, such as the raising of fingers in slow scale practice. I think that videotaping yourself practicing is very effective, good job.
Concerning arpeggios, my teacher doesn't restrict me to just the "normal" ones. We practice the "eleven chords" aspect. That is that there are 11 different arpeggio structures played in succession, begining with C major and ending with a diminished 7th chord, with the fifth finger playing the octave, so like this: C, Eflat, Gflat, A, and C again. In music theory, the A is written as B double flat for theory reasons. I practice arpeggios in many many ways to ensure stability and speed. I love to whiz through them, but better not because that is not good for stability.
When practicing scales, arps, and chords, I not only play them in parallel motion, but also in opposite motion. With scales it is much easier, so don't forget to do that.
Practice chords. Before going to arpeggios, I practice chord structures. For example, the E major. I grab E, G sharp, B, and E again, holding down E and B, I strike the other 2. Then in successions eight notes, then treoles, then sixteenth notes. Then the other inversion, then another. After that I move on to playing short arpeggios, then broken, then long. After that, I move on to chords.
Then I move to other technical excercises.