Snippets

You likely will improve your sound if you tuck your upper lip in a bit (not over your teeth, just against them).  Not sure exactly why, but it works most of the time.

Don't take a breath immediately before blowing long exposed note! You will blow "rich" oxygen into the clarinet, but after a few seconds the level of carbon dioxide in your breath will increase, causing the pitch to go up. The best thing to do if you have to start a long note "cold" is to take a breath, hold it for a few seconds, then sound the note. (Corrolary: Don't try to tune any note unless you've held your breath for a bit first.)

Clean your tenon sockets with something other than your swab! You don't want cork grease to be introduced into the bore.

There's an alternate fingering for clarion Bb (above the staff), which is a pure note on the German system, but not so good on the Boehm, that I use for this change from G or G#:  I play the G or G# and, to get to the Bb, I lift the left-hand middle finger. The Bb isn't pretty, but it works going that fast. It's a handy thing to know tremolos between these notes or in fast passages.