Be relaxed! If you are tense in the audition, they might think you will be tense in the show. Also, smile and have fun with it! Be enthusiastic and just trying to get in character. Dont let being nervous take over. Just relax and have fun with it and I'm sure you'll get the part. Good luck!
Come up with back-up lines that are Ok with the director so if you forget your original lines then at least you'll remember your backups :)
Get into your character. Sometimes distracting yourself from your nervousness, and really getting into your character, works the best. Be enthusiastic, too! And dramatic, dramatic is key. :)
Have fun with it! Dont get too carried away with being nervous and stuff. Just be relaxed and have fun. Shakespeare plays are the bomb :)