My mom has been a singer for 40 years +. She began as an opera singer back in the 1950's in high school. She was so good she had a scholarship to sing opera at Julliard School of Music. She declined it and married my dad at 17 y/o. Nevertheless, all of her opera training carried over into her singing of jazz/pop etc. She teaches voice lessons in her home. Here are some of the things I've heard her say to students:
1. Sing from your diaphram. BUT, don't "hold" your breath. Many times when she tells novice students to pull in their stomach muscles, you can see their chest puff up as it does when one takes a deep breath and holds it. It's a constant "tummy pull" NOT a chest expansion and taking in air to save for notes you're getting ready to sing.
2. Drink lots of water. DON'T drink cold water---drink only room temperature or luke warm water. Constantly doing this keeps mucous down and sinuses clearer.
3. Use the microphone--sing into the cone of the mic and pull it back a little on your louder notes.
4. OPEN YOUR MOUTH. Forming your mouth correctly to sing the correct vowels and syllables keeps the air from backing up on your throat. It's like it's trapped with no where to go if you don't open your mouth.
5. Don't try to look cute--smiling and singing. If you have to get ugly, do it--just get your mouth open.
Now, my mom can sing with a cold, a fever, etc. Singing is as easy as talking to her. In churches I've played in or choir singers I've talked to say things like "I can't sing more than 3 or 4 songs" or "We're not singing much this morning because we have to sing this afternoon at another program---we're saving our voices." My mom would say, "Saving it for what" :?: :!: She can do a gig and sing 40 songs during the gig like it was nothing. Proper training and breath control.
Find a vocal coach in your area who teaches things like this and you can learn to sing all day and all night.
Stay encouraged.
Lisa
