I went to a song circle where it was difficult to back out and sang in three different keys for one song. Fortuneately somebody else knew the song and started singing along and that helped. What was just as hard was forcing myself out the door to the circle the next week. Rest assured you will make mistakes and forget words and start off in the wrong key or on the wrong note and start too fast or too slow, but if you keep going and going to any place like a song circle or open mic, you WILL get better and less nervous of the audience. For me I knew I either had to get out and sing in front of others or spend the rest of my life kicking myself in the behind for not doing it. Now I can cheerfully sing along with others at parties, instead of being painfully shy about it and getting drunk and therefore singing worse.