I have been playing clarinet for our years now and I've learned Artie Shaw's Clarinet Concerto at this point, but I always had this problem. I could never cleanly tongue. It actually sounds so repulsive to tongue that I actually have defaulted to using my lip, which might not sound as good as it could be but, managed to be somehow better than all the other students which have been playing since elementary (I started my first year of high-school, this is my final year). I want to change my ways and so I searched around and I found no assistance for my particular problem. Then I read this guide on clarinet basics that mentioned how to start notes. It had 3 listed forms "Tah", "Dah", and one that I've never seen before "Hah". I was actually surprised that sliding into a note had it's own articulation. So I tried it with one note and It sounded better than my tonguing. Appalled I tried it again, this time I tried to play an exercise counted "1-y-an-da, 2- - - , 3 -y-an-da, 4 - - -, 1yanda, 2yanda, 3yanda, 4 - - -". I noticed that the sixteenth notes sounded familiar. Then I went back to tonguing the excercise and I realized the problem, or at least a hint. The only difference between tonguing and using only air, is tonguing has a definite start. Even I'm lightly tonguing a note that I'm holding out, it sounds like I'm just using a focused huff of air. My tongue is flat for the tip. and it is in fact very thick. When I stick out my tongue, it hardly can go over my slightly bigger than average bottom lip. I really hope someone can give me some sort of advice.