Sing the vowels "a," "e," "i," "o," "u" -- start with near whispers and raise the voice gradually with very exaggerated facial expressions. Feel the rumbling and vibration of the sounds as they elevate and descend. Fill the lungs with breath and hold a single vowel with the mouth fully opened, then raise and lower the sounds. Imagine the sounds filling different parts of your body, such as the "i" pronounced as "ee" rising high into your skull. Move the sounds and feel their resonance in your face and chest. Replace the lyrics of a favorite song with vowels, but "act" the song as though you were on the stage at the Hollywood Bowl.
The sound "ing" gets quite a lift here. Individually or in a group, make the "n" sound and build it up more and more until your breath is nearly out, then "toss" the last syllable "guy" very strongly at the ceiling or at other actors. Move around on stage, letting your body loosen up while doing this. Repeat it often. You can also do this while lying on the floor.
Choose a set of lines, maybe three. Your goal is to "dunk" them into an imaginary basket on the back wall of the auditorium or theater. "Aim" the words for a three-pointer directly at the center of the far wall, or "dribble" them down the aisle until you can do a "layup" into the basket. After experimenting with the variations, try to "sink" all the words of all the lines into the basket.
Place two people on opposite sides of the stage or theater, facing away from each other. Each is holding an imaginary phone. Begin by stage-whispering dialogue or practice lines into the phone. You can also improvise all the words. The person on the opposite side must listen and indicate a loud "Hello" each time she can actually hear the other person. Bring the whisper up, and more up, then move into normal speaking voice. When you get 10 hellos, hang up. Dial a new number by switching partners.