First of all, be calm and be yourself tomorrow. Your nervousness might make you look uncomfortable around her and might put her off.

Carry on with your initial plan as it's from your heart and it should reflect your true self.

Don't expect her to jump up and down and tell you that she feels the same way (though that would be nice). Give her time if she need's it and as said by others, be prepared for the worst.

With that being said, all the best for tomorrow. May your love life be blessed and hopefully you will share a good news with all of us tomorrow. Keeping my fingers crossed for you.