1. Jutting the chin forward on high or loud notes
Doing this tightens the throat, compromises pitch and range, limits expression to a painful one
2. Crushing the chest (even a little bit) to squeeze out power
Doing this plows too much breath into the vocal cords, limiting ability to control the voice, also affecting tone, pith and range. The inhale is even affected because it's taken too high in the chest since that's where the squeeze is going to come from.
3. Not communicating lyrics clearly
This drives me nuts... especially if the music makes me want to actually know what the song is about. You lose your audience quickly since you're not communicating anything they can understand.
4. Dead eyes with no expression
Eyes are very important to subtle lifting and opening in the throat. Dead eyes mean dead tone, limiting range and ability to communicate.
5. Entertaining with no artistry (singing at the crowd without the slightest indication you know what the lyrics mean)
The best singers are artists first, entertainers second. It's a subtle thing, but you can tell the difference by whether or not the singer moves the heart.
Sooooo.... what's the worst vocal habit you've seen (or have !)?