last friday and saturday i played in front of about 300 people with my band, so 600 total. the most id ever played for before that was maybe 30
the thing is, you have to believe that you are good, and tell yourself that. get pumped up before you play. and then, just act like you are practicing at home and get into it. feel what you are playing. i was a bit nervous the first night, but i got over it and it was great.
if you think you are good, make everyone else believe it. dont worry about what they MIGHT think, play your best and KNOW what they will think when you are done.