Music theory practice is essential to learning more and getting better at music theory, but how do you do it? This is similar to practicing math in a way. BUT WAIT, DON'T LEAVE YET!! This can be fun and interesting. This is like math you can play on your instrument.... Ok, so I lied, it's really not like math at all. But you go about practicing it the same way.
To practice music theory, you have to have exercises, or problems. Normally these come in the form of the music we play. Whenever you play music at all, you are working on music theory practice. Playing certain note combinations in certain keys will train your brain to recognize these patterns and apply them to other musical situations later.
However, let's say you want to learn faster. Just playing the same ole music you are used to isn't enough. This is where the exercises or 'problems' come into play. Give yourself little quizzes to work with.
Say you want to work on scales. Drill yourself.
What are the notes of a C major scale. Check.
Ok, now what are the notes of a G major scale. Check
Ok, now what are the notes of a D major scale. Check etc...
Say you want to work on arpeggios. Again drill yourself.
What are the notes in an A major chord. Check. Now stack those in an order. Check
Next key, etc...
NOW THIS IS IMPORTANT!! When you are studying these, it's ok to just go through them in your head if you are waiting in line at the bank, or bored during English class. But at some point, MAKE SURE YOU PLAY THESE ON YOUR INSTRUMENT. If you play multiple instruments, it would be ideal of you could do these on all of them. (Or maybe a separate exercise for each one, then rotate them every day or so, so that each instrument gets balanced.)