As a huge Disney fan, I have so many!
Utilize Fast Pass- its best if you get them earlier in the day as they often go as the day goes on.
Confirm all dining reservations- take all confirmation numbers with you.
If you are staying on property utilize Extra Magic Hours.. I know some are against EMH but I always enjoy them.
Be sure to catch Wishes, Fantasmic, SpectroMagic, and IllumiNations. They are all my favorite shows!
If is it taking place during your visit, I'd suggest going to the Pirate and Princess Party at the Magic Kingdom. So much fun!
If I think of anything else, I'll let you know.
Where are you stay?
ETA: How long are you going for? I know you'll have a great time. I'll be there on March 14th!