I find that singing long, low notes quietly while you are taking a shower (lots of moisture in the air) and gradually moving to middle range notes (but don't work the upper range) gets the vocal chords lubricated and loosened up while you are getting ready for your morning gig. And drink at least a pint of water after the shower.

And all of Taike's tips are spot on..... Plenty of sleep, plenty of water, you should have no problems.