If you are playing an instrument, it's likely that you want to get better at the one that you are currently playing. There are a variety of things that you need to be doing if you really want to improve. Learn what things that you can work on that will make getting better at your instrument much easier.
First of all, you need to have something that you are really trying to improve. Many times there is practice without a real technique or goal that you are trying to master. Make sure you have solid exercises for specific goals that you are always working on.
Think about practicing your instrument when you are not even playing it. There is a huge mental side to any instrument. Learn how to do this will help you improve even while not touching the instrument.
Go to YouTube or another video site and search for people who play the instrument of your choice. Typically there are many good instructional videos as well as very good players that will inspire you to do better. Try the same techniques that you see in the videos and try to play like them as best as you can.
Learn music theory. Do not make the huge mistake of not learning this discipline. This will give you a better understanding of music which can give you a better understanding of how to play your instrument.
Take what you learn from music theory and start to practice scales. There are hundreds of them to learn and practice on your instrument. This will give you a better understanding of the relationship of notes in a song making it a bit easier to play.
Start to practice with a metronome. This is a device that is designed to keep a beat. This will help you with your rhythm as well. Take the metronome and gradually increase the speed so that you will be playing faster and faster.