I take very little mouthpiece. Perhaps 1/4 of an inch.
I tried for years to "take more" with some good effect, but also causing tightening my jaw, an untenable habit.
Then I realized the amount of mouthpiece taken is not nearly as important as how relaxed the jaw is.
Here's a quick primer to find the best amount of mouthpiece taken-
- Beginning with a "slack" jaw, let your jaw hang lose, lips relaxed but parted.
- Gently. And I mean gently. Gently form a pseudo-embouchure, keeping your jaw lose.
- Gingerly insert the tip of the mouthpiece and snug it into your floppy unsealed embouchure. (bottom lip over bottom teeth and top lip on mouthpiece, except double lip)
- Delicately seal the embouchure.
- Maintaining a slack jaw, softly blow an open g.
That is your ideal angle of interaction with the mouthpiece.
You may not sound great on the soft g, but that's not the point. Firming up embouchure and voicing will add quality to the sound. Maintain the soft, slack jaw as you zone in with your embouchure. Prioritize.
Another useful test for finding the "fulcrum" (most efficient place down the mouthpiece facing for controlling the reed)-
I learned this from Richard Hawkins, clarinet professor at Oberlin.
To test and find that fulcrum, play an open g. Take a bit more mouthpiece, and play another open g. Continue taking in mouthpiece until you squeak. Back up a step and there you are.
You may end up with slightly different amounts of mouthpiece with each of these tests. That can be remedied.
Starting with the slack jaw method and find that point of contact. Then proceed to the fulcrum test, but instead of opening your mouth more, gently snug it open with the amount of mouthpiece. This snugging pressure is accomplished by giving a little more "lift" from the right hand thumb holding up the instrument.
Gently blow an open g.