Walt Disney World offers daytime and night time parades. If you want to see one, arrive where you would like to be AT LEAST 30 Minutes prior to the start of the parade or if you go during peak season, arrive about 45 minutes earlier.
Magic Kingdom: crowds are usually thinner in Frontierland than on Main Street. The bridge between Tomorrowland and Main Street is a great location to watch the Fireworks.
Fantastimc(Hollywood Studios) has great seating all around. Don’t try to get yourself a seating are to leave quickly it just doesn’t work that way. I recommend sitting towards the middle or back to get the best views. You can also sees these outside of the park, just can’t hear the music.
Illuminations (Epcot) Try not to get under a tree that will limit your view and if the wind is blowing in your face you could get smoke from the show. Best spot to avoid smoke is Norway/Italy side.
Animal Kingdom: Between Africa and Asia offers great views and shade too