Get a good night's sleep the night before, eat a sensible breakfast, take a friend or two along, take a backup instrument or at the very least spare strings, stay hydrated, avoid alcohol (and etc) until you are all done.
"This young wine may have a lot of tannins now, but in 5 or 10 years it is going to be spectacular, despite the fact that right now it tastes like crude oil. You know this is how it is supposed to taste at this stage of development." ~ Itzhak Perlman
Ι second everything said before
A couple of other things you should think about is actually understanding that you may have forgotten how it's like to perform in front of other people, which is great and thrilling as well. But sometimes, if we haven't done so for a long time it can be confusing, make us feel nervous or even get distracted
I would either practice on "how not to get distracted" by anything going around while I would practice. I understand that there can be lots of methods, either looking at your instrument, your hands, or looking at nowhere with an empty gaze.
Some of these could also be distracting so you should find out which works for you. I would also ask some friends to attend an informal "rehearsal" and ask them to be noisy if they like.
you just make it like rock n roll. Enjoy everything.
Either way good luck, and congratulations for picking up the violin again
Daniel - I completely overlooked the obvious about having spares. Cheers.
TonI - Thanks. Music always comes first.
Here's - That's a very good point. I remember the nerves taking over when I was wee and loosing the place on the sheet music constantly. I have been standing at my windows while practicing and it is fairly distracting with the cars and noise. I like the idea of having friends over, may just do that. Thanks.