OK... well I would first decide when I want to go. If you can AVOID the 2 week Christmas break,Spring break, Presidents Day,Memorial Day, 4th and the REALLY HOT

June,July, August months. We have gone twice the 3rd week of May(left the Friday of Memorial Weekemd) and the middle of October for the Food/Wine festival and we are leaving again the last week of April-the first week in May. I realize the kids will need to be taken out of school but I checked the school schedule and plan around State given tests and finals.
Then decide what your budget can be for your tickets. We have done the Ultimate tics that include EVEYTHING including park hopping, water parks and Disney Quest. BUt since this is our very BUDGETED vacation coming up we are staying off-site in a suite I booked online for 68.00/night and we are dong just the 7 day BASIC passes at 200.00/each. With no hopping,water parks or anything. We have included extras in our budget IF we want to go when we get there.
The suite also serves free breakfast. You need to decide how many sit down restaurants or character meals these will cost 20.00-30.00/per person.
And of course go buy a Disney planning book..either Disney's burnbaum or Passporter or the Unofficil guide, These books help ALOT!!
Have Fun planning!!!
