1. If you don't understand your vocal technique, you won't be able to use it. Speaking and singing really are as simple as breathe, support, imbibe sound; while looking unconcernedly at an imaginary horizon. Having a perfect technique means that you can produce any note in your range, at any dynamic, at any speed, on any vowel shape, preceded and followed by any consonant or cluster of consonants. Vocal exercises should do no more and no less than facilitate your doing this.
For breathing, take a basic posture that's a happy medium between guardsman being square-bashed and camel about to spit, then coax your ribs away from your body and imagine that your lungs are in your shins.
For support, I incline to Dame Joan Sutherland's view that it's a lot like being sick.
(Just now, recreate the physical process of being sick. Then think how in reality you wouldn't want to get in the way...)
For resonance I imagine that I'm drinking my voice, tasting and smelling it as it flows downward.
2. Always warm up before using your voice. I don't care if you don't think you need to. Don't quote instances of performers saying they don't need to. Verdi wrote a warm-up fugue every day. That's good enough for us.
3. Never speak or sing without supporting your sound. Your whole body must be involved in it. As examples of ways to describe the sound: flowing, limpid, nuanced and focussed will always be preferable to: Like having rusty Meccano sprocket wheels run up and down my perineum.
4. Do your voice work first thing, starting with spoken voice exercises. If you have nothing to say, you'll have nothing to sing. Whichever exercises you use, start with the physical setup, then breathe into support, exhale from support, speak the neutral vowel shape, open into "ee" then "ah", then use consonants. Go from the beginning of this process when you switch to singing.
5. You are either using your voice in this thoughtful manner, or you're silent.
6. Better still, you're asleep.
7. Stop clearing your throat. If you have chronic catarrh, you may have to give up dairy. Soya milk becomes palatable after three months.
8. When in a theatre company, make your own noise and leave others to make theirs. I mean this in both the real and in the metaphorical sense.
9. Accept nerves, rather than displace, disguise or tamper with them.
10. Eat healthily - never a main meal within five hours of going to bed - have a bottle of water practically grafted onto your palm, drink alcohol sparingly, don't smoke.
11. Remedies for stress include: cold showers, aerobic exercise, meditation, masturbation, lavender.
12. I agree with Lady Boxe, The Diary of a Provincial Lady, that the saline-douche habit needs to be fully reinstated. Unless you have glue-ear, or similar.
13. Don't have glue-ear, or similar.
14. Cloves are antibacterial. I suck one morning and evening. The evening clove helps me become suitably ruminatory watching Judge Judy.
15. Don't eat Vocalzones/Lockets/Fisherman's Friends or similar.
16. Keep your feet warm and dry and your head cool. Wrap up when leaving a warm backstage area to go out into the cold. Don't let rain soak you to the skin.
17. Colds season starts when the central heating does. Counteract drying effects with bowls of water near radiators or wet towels hung over doors. If you wake up with a dry throat, dunk a sponge in boiling water and hold it to your mouth before starting on your voice work.
18. If you catch cold, first and foremost keep it to yourself. Don't take over-the-counter drugs to disguise its symptoms. You're meant to have a temperature, soreness, aches, etc. Deal with it. A few times a day inhale nearly boiling water - no need, actually, to put anything in it - but stay silent and indoors for at least two hours afterward. Otherwise, rest and entertain yourself. Read my blog. Watch Judge Judy. I would say you can speak and sing if you have to unless your cords are waterlogged. Keep an eye out for the cold persisting or dropping to your chest, as then you may need to see a doctor.
16. Never read your reviews.