I think there are several factors going for your daughter..her age being one. Not that it excuses any behavior issues , but it does help to put it in some context. Yes, our roll as parents is to guide and teach, love and nuture..I believe we do that largely by example..expecting No misbehaving and the punishment being a spanking, IMHO is completely inappropriate response.
Keep in mind when kids are at WDW it is very overstimulating...not to mention adding the factor of being utterly and completely excited about the experience. Given this, kids may even have less patience then before. I think that setting clear expectations before you go to the park is a great idea. If she completely melts down ...take a break...go back to the resort/leave ..find a quite place to sit and spend some time together. I think that taking items to help pass the time you are in line is also great. I plan on taking bubbles and other small toys to help pass the time. Use a fast pass when you can. If the line is really long, explain to you daughter that if she really wants to go on the ride that she will have to wait..and it might be awhile...give her the option as to whether or not she wants to wait. Once in line, if it becomes too much, you can always look for a CM and ask them to show you the way out.
Take your cues from your daughter, don't try to put too much into one day. Try to hit the most popular rides during the early hrs b/4 the park gets to crazy.
Most of all remember that this is suppossed to be a fun and wonderful experience. Does this mean you don't redirect and consequence misbehavior when appropriate....NO...but it means that you look at the situation from the eyes of your child and you try to provide the direction she needs in a loving and caring manner.
Wishing you a wonderful trip.....
edited to add: I really like the suggestion of the positives being given too!! And yes..follow through is essential..if you say it, you must be willing to follow though and do it!
here is a website with some cool age specific activities too
http://www.momsminivan.com/