Building a magical fantasy world...

So I've decided to attempt a character-driven story set in a magical fantasy world... but how do you build a magical fantasy world that is both compelling and uniquely yours? How do you weave in fantasy tropes (magical trinkets, a perilous quest, etc.) without unwittingly copying everything that's come before?

Brandon Sanderson talks about how The Lord of the Rings changed the landscape of fantasy literature forever—and perhaps not for the better:

[Tolkien's] work was so revolutionary that the market couldn't deal with it. Readers wanted more books like LotR, but other authors weren't ready to produce high fantasy yet. The only thing they could do was try and do what Tolkien did.

But they didn't do what Tolkien did. They didn't create a new world, with its own mythology, its own society, its own technology, its own races and creatures. This wasn't their fault—they just weren't ready to jump to that level. So instead they applied their considerable creativity toward copying Tolkien. Instead of creating true high fantasy, everyone created more low fantasy—but they used Tolkien's world as a base instead of our own. The result was a kind of tainting of the entire genre, a 'Tolkienizing.' Fantasy didn't mean 'the genre where the author creates his or her own unique setting.' It meant 'the genre where the books include elves, dwarfs, wizards, and quests.'

(Link to the rest here.)

Well, crud. And conversely, if I am going to build an entire fantasy setting that's uniquely mine, owing nothing to Tolkien et al.... where do I start? The Science Fiction & Fantasy Writers of America has a great series of fantasy worldbuilding questions to ask yourself... but now there's the threat of being overwhelmed by the scope of this thing before I've even written one word. For example:

• How are the continents laid out? If there is more than one moon/sun, how does this affect winds, tides, and weather generally?
• How much land is there, and how much of it is habitable?
• Is the axial tilt and orbit the same — i.e., does the world have the same seasons and same length of year as Earth?

I could of course just start writing the story and figure out these details later, but that's going to make for some tough writing.

Have you tried to build a magical fantasy world? If so, what was the experience like for you? What were some helpful things to keep in mind?