Deep in Frontierland (past Country Bears,) arrive 15 minutes before the start-time of the parade.
It originates back there, yet few guests grab viewing spots there.
Another great spot is near Hall of Presidents in Liberty Square.
Just know that from anywhere other than in or near the Hub (or the southern end of Main St., you won't be able to see the spectacular, not-to-be-missed show that is actually projected on the front of the Castle, "Celebrate the Magic," which begins about 15 minutes before the fireworks.