Nerves yes always and everybody has them
quite normal use them to sharpen your performance.
Experience helps but it still happens

Practice a lot first rule.
That is why it shows up so often above all hail to those who say it

If you get the chance practice on an audience wife, friends, kids, the experience works
(My kids reported me for cruelty.)

Try not to get rushed about prior to your performance
Give yourself a minute or two to compose yourself before going on
Deep breathing prior to going on helps
Try and get the voice warmed up sing along with others

Booze - no you have enough on without being fuddled.
Afterwards you can drink to insensibility

An ice breaker is useful a good evening and this is a song by ....and off you go
Keep the intro short first time and that's probably good advice always
The audience is on your side and will forgive you and encourage you.

Take a glass of water with you if you are on any length of time

The Flight of the bumble bee in J augmented might be your party piece but start with something EASY.
40 verse marathons are not recommended
If it's a song the audience knows they will help you out

Try to relax and enjoy the experience the rewards can be great

Persevere

Good luck
Fantum