- Shouting over loud music in a bar/restaurant
- Smoking/drugs/excessive drinking
- 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.