10 great ways to ruin your voice
Shouting over loud music in a bar/restaurant
Smoking/drugs/excessive drinking
"Placement"
Belly breathing
Pushing or any other kind of straining
Believing that singing is like sustained speaking
Doing anything "from the diaphragm"
Neglecting the development of either the chest register or the falsetto
Depressing your larynx through conscious effort or by mechanical means
Most group warm-ups (Better to warm up alone beforehand, then lip-synch through the group drills)
I'll eventually blog about all these detrimental practices.
Add your favorite don'ts—or refute mine—by commenting to this post.