Practicing a musical instrument is the most important thing you can do to improve as a player. The amount of time you have to put in will vary from player to player depending on age, and ability. Everything worth doing takes time and effort and finding the motivation can be hard. Expect ups and downs in the process of learning and just keep going!
So you're ready to practice... now what? Learning how to spend your time effectively in practice can be a challenge, but with these tips you will be well on your way to successfully practicing your instrument.
Step 1: What will you do? Decide what you want to accomplish. Don't just play when you practice; work on something specific in order to improve. Do you want to focus on tone? Intonation? Rhythm? A particularly tricky section in a piece? Assignment material? Learn a new tune by ear? What you decide to work on will affect what you need in Step 2.
Remember also to keep short-term (what you will do today) and long-term (what you will be able to do in a month) in mind. This will also encourage you to practice often!
Step 2: Are you prepared? Do you have your instrument, music, a pencil, a metronome, a tuner, an environment where you can focus, and (most importantly) a ready ear? You must be ready to listen to yourself critically when you practice as it is just you and your instrument. You are your own teacher at this time!
Step 3: Warm-up "But I'm about to play! Why do I have to warm up first?!" Believe it or not, the warm-up is more essential to your practice session that the actual practice! After correctly and carefully putting together your instrument, make sure you play a wide range of notes so you know your instrument is in working order (not too many high notes; as you said yourself, you're about to play!), play long tones and faster patterns, an etude or two, and exercises in two or more keys to mentally and physically prepare yourself.
Step 4: Macro Micro Macro (big picture, small section, big picture) Start playing what you have decided to work on. When you hear something that does not sound the way you want, stop and focus on that section. Is it a rhythm? A pitch? Two pitches that never seem to sound right?
Remember that this is a learning process, so try not to get frustrated, and just go back to the beginning.
Go a little farther back and play it in context. Is it still a problem, or has it been fixed? If it is still a problem, find the new trouble spot. If it is fixed, move on until your critical ear hears something else it is not happy with.
Step 5: Reward! Congratulations! You got through your practice session. Your reward is to play something that you excel at playing, and then to cool down you and your instrument. Play mid-range long tones, focusing on the tone and intonation. Correctly and carefully clean and put away your instrument and accessories.
General Practice Tips - Practice slowly and relax - Have a good attitude; don't get on your own case if something doesn't go the way you want it to. That's what tomorrow is for! - Practice with full sound and good tone at ALL TIMES - Don't practice mistakes but CORRECT repititions - If you are tired or can't focus, stop practicing and come back to it later - Have a sound model; listen to recordings of great musicians for your instrument - Constantly check your posture, breathing, embouchure, hand position and instrument position