Going to Disney! Any advice?

Hi all!  This will be our (Santa/DH and I) first trip to WDW!  And, of course, that means I have questions!

What shouldn't we miss?  What should we do about dining - we have the free dining plan but I understand that you should make reservations in advance?  What restaurants are really worth it - of course, keeping in mind my that I don't eat huge portions as most of us do not.  Any shows that we shouldn't miss? 

Please, any tips and tricks and advice would be greatly appreciated!  

Thank you, thank you! I'm SOOO excited!  Even moreso now that I can get my tush on a few rides!