4. Be prepared! This is not just about practise a lot, but really know the music. Know the score and phrasing in your head. If something goes wrong, it will be easier to fix (plus, it will be easier not to fail somewhere).
To pretend one won't be nervous before an important performance is to deny normal human nature; this is especially true if a long hiatus exists before one's last gig. There is, of course, no substitute for practice, practice, practice. Know your program backwards and forwards, because at an actual performance, we all play less than perfectly.