Hi Les

In addition to all the good advice given above, there are two other things, almost contradicting one another, that can help at different times.
1. Look just above the heads of the audience, visualise a friend and sing to them.
2. Choose someone in the audience who looks sympathetic and sing to them.

I firmly believe though that if you have no stage fright whatsoever, it's time to give up. It does give you that extra dose of adrenalin that makes all the difference to a performance.

Good luck
Eddie