Clarinet mouthpiece. If you purchased or received a clarinet and play the mouthpiece that originally came in that case, you are in for a big surprise. The dirty little secret is that most stock mouthpieces that come with the clarinet are horrible, usually very free blowing for the very, very beginner clarinetist.Flight of the Bumblebee
BUYING A GOOD QUALITY MOUTHPIECE IS THE SINGLE BEST IMPROVEMENT YOU CAN MAKE IN YOUR CLARINET SOUND QUALITY. So, if you are financially strapped and cannot afford a clarinet now, search for some good mouthpieces. Clarinet-Now.com is a good place to start.
Starting with a good mouthpiece is important. I usually have my students try the Vandoren M-13 Clarinet Mouthpiece, Vandoren 5RV-Lyre Mouthpiece, and the Vandoren M-30 Mouthpiece.
Understand there are many, many, many more types of mouthpieces. But, these are a good place to start.