Vibrato takes 60% more breath to sing.

Audiences are soothed by vibrato.  Imagine you are soothing the audience while you sing vibrato.

Simple Vibrato

Vibrato should be practiced while using a metronome (on your phone).  Your vibrato cycles count must be in sync with the beats of the metronome.

Everyone can do it.  You must start small and practice a lot.  Take a song you like with a lot of vibrato.  Sing the vibrato part very very low in volume, just above a whisper.  Notice how Elvis lowered the volume of his voice when he sang vibrato.  After you are consistent with the tremelo, practice it at low volume ALL THE TIME: when driving, when at Walmart, when at the grocery store.