Take a Scientific approach to practicing:
Define the problem (what do I want this to sound like?)
Predict the cause (what is causing it to sound like this?)
Hypothesize (If I change i.e. the attack and length will it change/produce the sound I want?)
Test (try out your idea!)
Analyze (what changes seem to work best?)
Implement the best solution (make these changes permanent)
Monitor implementation (do these changes continue to produce the results I’m looking for?)
How much should I practice: (Mr. Mendez, FM High School Orchestras director) for more tips click on thier link.
"Instead of mindless trial and error, take an active and thoughtful process of experimentation with goals and hypotheses. Proper practicing is often slow, and involves repetition of small and very specific sections of your repertoire instead of just playing through (e.g. working on just the opening note of your solo to make sure that it “speaks” exactly the way you want, instead of playing the entire opening phrase).
Deliberate practice involves monitoring one’s performance (in real-time, but also via recordings), continually looking for new ways to improve. This means really listening to what happens, so that you can tell yourself exactly what went wrong. For instance, was the first note note sharp? Flat? Too loud? Too soft? Too harsh? Too short? Too long?
Let’s say that the note was too sharp and too long with not enough of an attack to begin the note. Well, how sharp was it? A little? A lot? How much longer was the note than you wanted it to be? How much more of an attack did you want?
Ok, the note was a little sharp, just a hair too long, and required a much clearer attack in order to be consistent with the marked articulation and dynamics. So, why was the note sharp? What did you do? What do you need to do to make sure the note is perfectly in tune every time? How do you ensure that the length is just as you want it to be, and how do you get a consistently clean and clear attack to begin the note so it begins in the right character?
Now, let’s imagine you recorded all of this and could listen to how this last attempt sounded. Does that combination of ingredients give you the desired result? In other words, does that combination of ingredients convey the mood or character you want to communicate to the listener as effectively as you thought it would?
Few musicians take the time to stop, analyze what went wrong, why it happened, and how they can correct the error permanently.
Keys For More Effective Practice
Keep practice sessions limited to a duration that allows you to stay focused. This may be as short as 10-20 minutes for younger students, and as long as 45-60 minutes for older individuals.
Keep track of times during the day when you tend to have the most energy. This may be first thing in the morning, or right before lunch, etc. Try to do your practicing during these naturally productive periods as these are the times at which you will be able to focus and think most clearly.
Try using a practice notebook. Keep track of your practice goals and what you discover during your practice sessions. The key to getting into the “zone” when practicing is to be constantly striving to have clarity of intention. In other words, to have a clear idea of the sound you want to produce, or particular phrasing you’d like to try, or specific articulation, intonation, etc. that you’d like to be able to execute consistently.
When you figure something out, write it down. As I practiced more mindfully, I began learning so much during practice sessions that if I didn’t write everything down, I’d forget.
4. Smarter, not harder
Sometimes if a particular passage is not coming out the way we want it to, it just means we need to practice more. There are also times, however, when we don’t need to practice harder, but need an altogether different strategy or technique.
I remember struggling with the left-hand pizzicato variation in Paganini’s 24th Caprice. I was getting frustrated and kept trying harder and harder to make the notes speak, but all I got was sore fingers, a couple of which actually started to bleed. I realized that there had to be a smarter, more effective way to accomplish my goal.
Instead of stubbornly keeping at a strategy or technique that wasn’t working for me, I forced myself to stop practicing this section altogether. I tried to brainstorm different solutions to the problem for a day or so, and wrote down ideas to try as they occurred to me. When I felt that I came up with some promising solutions, I just started experimenting. I eventually came up with a solution that I worked on over the next week or so, and when I played the caprice for my teacher, he actually asked me how I made the notes speak so clearly!"
"It doesn’t matter if we are talking about perfecting technique, or experimenting with different musical ideas. Any model which encourages smarter, more systematic, active thought, and clearly articulated goals will help cut down on wasted, ineffective practice time. After all, who wants to spend all day in the practice room? Get in, get stuff done, and get out!" (Mr. Mendez)