My recommendation?
Depends on how much of the special entertainment you want to see.
The Parade runs twice. 9:15 and 11:15.
Fireworks are at 10:15.
There is also a really neat Villians stage show at the Castle at 8:30, 10:45 and midnight.
If you are not interested in the Fireworks or the Villians show, avoid Main Street or the Hub.
Show up about 30 (45 to be “safe”) minutes early to Frontierland.
As you enter Frontierland from Liberty Square, on the left just past the Shooting Gallery, you will find rockers and a planter / seating platform. The elevation gives you a good view, even when seated, of the parade.
If you are interested in the other two shows, I would recommend snagging a spot on the hub near the partners statue, or the seating outside Casey’s or the Plaza (umbrella seats). Be sure to buy some snacks so you aren’t just “camping”! You can see the fireworks, then the Villians show from there, then work your way to better seating in the general area to view the Parade.
Though my kid has never wanted to do it this way, I would aim for the later shows. Start with Fireworks at 10:15 somewhere around the hub. Then make your way to Frontierland (via Adventureland, I would venture) for the 11:15 Parade. Then work back across the Liberty Square bridge to the hub to watch the midnight Villians show.
One thing to note is that, with a few exceptions as you get closer to Halloween proper (and even then), the crowds are significantly reduced from a normal day. So, finding a good viewing spot isn’t nearly as difficult as you might think!
Some have mentioned the “seating” in Liberty Square. Aside from maybe Liberty Tree Tavern (I think the market blocks that view, 99% sure), I suspect they are referring to either the seating by Sleepy Hallow, the planters outside the Christmas Shop, or this place just outside of Hall of Presidents (to the right as you are facing the attraction, and yes, this picture is from this years Halloween party, about 10 minutes before the later parade was about to start. I took this picture last Tuesday):
The planters are reserved seating for disabled guests, and will be monitored and roped off.
Sleepy Hallow seating is not elevated, and your line of sight will be blocked.
But, these rockers by Hall of Presidents are a possibility. I don’t think they would give the “best” view, but it is rather quiet back there!
But, I wouldn’t recommend Liberty Square, personally. Because of the parade route blocking the area twice during the night, and proximity to Haunted Mansion, this area tends to get very congested during the party. Frontierland, for the parade, is far better.
Have fun!