Arch your eyebrows! Sound silly but it helps. Study what other singers are doing. Another thing is be aware of your microphone. Frank Sinatra was a master of using the mike to his advantage. Your audience doesn't need to hear your intake of air or other incidental noises. You can subtly shift the direction away from your mouth for a moment and most folks won't be aware of what you are doing but will appreciate the quality of your vocals. Bringing the mike in closer or away will also effect your vocals. If you have a mixer, have a good one as someone who knows and understands THAT craft, can have a profound effect on your singing. Let your mixer do the "LOUDER"!