Another thing to avoid is extensive speaking. Normal speaking is surprisingly detrimental to ones singing voice.

Other folk remedies for voice include flat, room temperature Coca-Cola. I don't think anyone has demonstrated efficacy of any of these techniques, but another big factor in effective singing is mental state. If a placebo ritual helps get you in the correct frame of mind to sing, then it might just be worth doing. The destructive alternative is to get intoxicated before a performance.