I would start by choosing your dates and resort, then going from there. I planned our first trip for our family of five last year

. There is plenty of great info on the disney world website and these boards, things like FP+ info, dining info, etc.! Once you have your date and resort you can look at crowd calendars and park hours and decide which parks to visit each day, as well as which attractions you want to do in each park. One thing I really wished I had done before going was study maps of the park layouts. We knew everything we wanted to do but spent a lot of time in the parks looking at the map trying to figure out where things were!