One must remember singing is as much about your habits between vocalizing as during. I've seen many so called pro who do nothing all week and then want to know why it doesn't work right on friday night when they hit the stage.
1. You should stretch your tongue several times a day, your throat as well
2. You should re-place and re-focus your voice and placement continuosly throughout the day
3. You should speak in different registers ,tonalities and placements throughout the day to maintain agility
4. you should breath fully and deeply (retain control of your breathing) at all times
These things will also help your speaking voice and prevent muscles from constricting between vocalizing.