How do I avoid straining?
Yawn. No, seriously.... don't just think about yawning and say you did it. Actually do it. Feel how open your throat becomes? THAT is what you want when you sing. Think about separating your back teeth fairly far apart, and smiling with the corners of your mouth.
Next.... remember all that crap about 'drop your jaw when you sing?' The old "open wide and exaggerate your vowels?" Forget it. Years and generations of bad advice from singing teachers passed on from their singing teachers. Why is it bad? Well... make an "Ah" sound while opening your mouth real wide, and drop your jaw as far as you can. Where do you feel the most tension? Your throat, you say? Hmmmm.....
How can I tell if I am straining?
The "straining checklist:"
Watch yourself in the mirror. (all singers are vain.... go ahead... you'd LOVE to watch yourself sing in the mirror, no? hahahahahaha)
- Are you turning red?
- Do you see veins popping out, especially in the neck area?
- Do you look like a chimpanzee squawking out a battle-cry?
- Singing should be natural and appear effortless. After singing, do you feel like you've just run a 7-minute mile?
- Does your voice sound tight, raspy, gravelly, compressed, squeezed out, etc?
If you answered yes to any of those, you are most certainly straining.
How do I sing hardcore, scream-o, death metal, etc?
These genres of music use a range of vocal effects with enough frequency that you are asking for trouble with your voice. If you accept that and are cognisant of the risks, and it is still what you want to do, then I would advise studying with someone who does that particular genre. Very few of those singers last very long, though, so beware.
That said, the Bel Canto technique can be and is applied to nearly every other style of singing imaginable. If you are doing limited screaming and growling, knowledge of the BelCanto technique can carry you through the rest of it, minimizing the risk of damage to your vocal cords.