Clarinets- focus on using tonguing as you play. For correct tonguing techniques, here are some resources to help you practice.
https://www.youtube.com/watch?v=-Y4Hfvm0Y4U&index=6&list=PL561317843105C8E9
Also work on making sure that you hold your cheeks in as you practice. Making that 'sour lemon' face will help you to firm up your chin and keep your cheeks from puffing out.
Use a mirror to help you see if what you are doing matches the pictures and videos you see.
https://www.youtube.com/watch?v=-Y4Hfvm0Y4U&index=6&list=PL561317843105C8E9
Also work on making sure that you hold your cheeks in as you practice. Making that 'sour lemon' face will help you to firm up your chin and keep your cheeks from puffing out.
Use a mirror to help you see if what you are doing matches the pictures and videos you see.