Skipy, do you play an instrument to accompany yourself or do you rely on others or do you sing unaccompanied? Whatever the case the trick to singing on key has much to do with choosing the right key for the song for your voice. I have limited vocal range so the key that I choose is critical. I do play guitar well enough to accompany myself and with my trusty capo can quickly find the right key. I am often reluctant to have others play along without a bit of rehersal because they can often mess me up even though they are better musicians than myself. Always know what key is best for the song you are going to sing and don't let others choose it for you. As Kendall suggested earlier, practice with a recording device before performing in public. Also choose a song that you know well and that you are comfortable with and practice, practice, practice. You can do it!