Here is a video I created with a performance technique called "The Off-stage Bit."  It literally refers to a process of preparing your song by developing an imaginary scene and character that you immerse yourself in as you sing.  Think of Method Acting.  This allows you to avoid performance and audition jitters by focusing on something very proactively.  But it requires practice, and doesn't replace technically preparing your music and your voice.  I hope you enjoy it!