We start out by looking at the park hours. Always look to see which parks may be closing early for special events. We usually do our first full day and last full day at Magic Kingdom. Why? It's iconic Disney! (If park hours above agree).
Next we look at the restaurants we would like to eat and see what reservations you can make. Table service dining reservations can be made 180 days out.
After that we work on fastpasses, 60 days out of on site and 30 days of not.
If dining and fast passes match with hours, we are golden. If not, we just adjust. A trip to Disney takes a lot of planning (in my opiniom). The more planning and adjusting you do will make the actual vacation run smoothier, not smoothly.
You can also just wing it, sometimes we just change our plans at last minute and that's okay, too. It's a vacation, you will make magical memories no matter what!!