There isn't a secret behind warm-ups! Warm-ups are not designed to trick you! So do them!
S T R E T C H I N G
Stretching allows the body to relax and relieve the tension you might have gained throughout the day. Obviously, we know that we use our vocal vocal cords to sing. But, did you know that we have to use the diaphragm to sing also? This is why we have to stretch the torso area too. If you do this every time we sing, then the diaphragm will become stronger. If you stretch over time that your voice will become stronger and you can sing longer with only one breath.
YAWNING
Choir class is probably the only place where you can yawn and the teacher won't give you dirty looks. This is because yawning is considered a warm up because it opens the throat and works the throat muscles. In singing, especially choral singing, an open throat is needed because it creates an open sound.
SCALES
After you are all warmed up, then you can start singing by practicing scales. A scale is a group of music notes that are in ascending or descending order. When you practice scales at different notes, it allows you to recognize where notes lie and the different tonal sounds associated with it. You can also hum or sing on a neutral syllable up and down the scale which also helps a lot too.
These are just some of the basic warm-ups that you need to know. If you warm up every time you sing, then, over time, it will preserve your voice.