(This excerpt was taken from a barbershop workshop...)

THE INSIDE SMILE

Do you remember being in church or at some other 'dignified'
function and suddenly think of a funny story? It would not
be too swift to smile when the preacher was talking about
the crucifixion. You suppress it, but the INSIDE SMILE comes.
The pads under your eyes lift, maybe your nostrils flare, but
the best thing that happens is your oral cavity will open up.
The sound WILL come out. Your mouth doesn't have to look like
a hog caller's. Remember, any tension will be ruinous. The
lips away from the teeth will add any coloration you need.
You don't have to bust a gut. The sound will come out.

Another way of thinking about it is you want to smile to that
pretty girl across the room without your wife seeing you do it.
It is almost the start of a yawning sensation, but DON'T yawn.
The air will choke off. Don't be a deadpan, don't let the
corners of your lips droop. (I'll bet it will add 50 points
to your total score!)

NOTES: If your soft palate chokes off, you will lose the highs
and lows. You will go a key and one half flat, GUARANTEED. Keep
happy thoughts in mind. This will make the INSIDE SMILE come
easier. Try this: open your mouth about one fingers worth, and
turn on your INSIDE SMILE. Sing the vowels AY, EE, EYE, OH, OO,
just like a ventriloquist. All vowel sounds are formed in the
oral cavity.

THE VOCAL LINE

  1.) Your posture is correct.
  2.) Your breath is correct.
  3.) You have the INSIDE SMILE right.

These are the fundamentals. Now get the discipline to do it all
the time. Know what to do. You should now know how to do it.
Control is all important in breathing and technique. It evens
the tones out and makes each of the sounds equal to each other
in focus and resonance.

BREATH

Tone simply rides on the breath. Singing should be effortless.  
Effortless head singing will produce all the tones and volume
that is required, and you can sing all day without getting hoarse.
It does require practice, practice, practice; no doubt about it!

Remember your chest should expand outward, front AND back,
keeping your shoulders down throughout the breathing process.
Breathe in by pushing out your abdomen and just opening up your
throat or if time allows, draw the air through the nose. If you
make noise when you breath then you are NOT doing it correctly.
RELAX!

Do some homework: one half hour a day extra practice will do
wonders. One evening a week is not enough...