Warm up in every practice session. It is a time to get in the right mind set to practice. Some beginner warm ups are scales, long tones, and tonguing exercises.
"One of the biggest problems with students is that they will constantly play the same things: the things they play well." Playing the things you play well does not make you any better. "You MUST practice the things you are bad at, then move on once you have achieved mastery."
"Wynton Marsalis used to put a roll of quarters on the left side of his stand and everytime he would get something right he would move a quarter over to the right. When he had all the quarters on the right he was done. If he messed up, all the quarters went back to the left." While it's not helpful for students to keep practicing something once they have it learned, they also shouldn't move on before they have mastered it.
Practice every day. "For a very beginner 15 minutes a day should be fine." Once they've been at it for a few weeks they should go to 30 minutes. "Missing a day here and there is fine, but it can quickly escalate into missing a week. It's better to shorten a day than skip it." A mixture of playing resources will make practicing more fun and more rewarding. "Listen to professional orchestras, bands, and soloists."
It's not enough to play just the notes written on the page, it has to sound good and be musical too. When you get frustrated, walk away for 5 minutes. So when you come back, you're more likely to have quicker success. "Don't practice mistakes. Mistakes stick once they're repeated, so it's best to fix them right away."
Source of Information from http://www.classicalmagnet.org/music/practice.php