Nicki Sinclair said in
rec.pets.dogs.health:

firmly take hold, pinch against the skin and slowly twist
to the left, counter clockwise until there is the sound of
"snap".

Why do you you twist it CCW? This just results in a better
chance of the head being left in.

I inspect the tick to make sure I got the head and
then flush the darn thing down the toilet.

Yup, it's a good idea to make sure you extracted the head.

--
--Matt. Rocky's a Dog.