Other things to watch out for are allergies/hay fever, fatigue, and muscle tension.

Last but definitely not to be taken lightly, having respect for your voice will hopefully save you from a lot of unnecessary problems. Take care of it. And if it is what your livelihood depends on, then take even more care of it!

SIMPLE WAYS TO COMBAT PROBLEMS WITH YOUR THROAT.

THROAT FEELING TIGHT OR TENSE
The simplest way to release tension is to yawn. Just watch where you do it though - yawning during a performance is not a good idea! 

Chewing releases tension in the jaws. Again, chewing while on stage will not do your image any good so; it is best done while you are off-stage!

Opening and closing your mouth. Let your closed jaw hang open. This will help ease tension in the jaws.

Swallowing or drinking helps too.

A gentle neck massage can help ease tension from your neck and otherwise relax you.