Characters, What Makes Them Tick?

I've always been told that when introducing a reader to a character, the most important thing to do--first and foremost--is to establish their wants. Let the reader know exactly what they desire, even if it's a grilled cheese sandwich.

But is that it? Just because you know they want a grilled cheese sandwich doesn't make you want to flag them down on the street and say "Hey, wanna' go get a cup of coffee?" Just because I know they want something doesn't make me care any more or less about them--they're simply a person, a common, everyday individual. And interesting stories aren't--as much as we'd like to think they are--about common individuals. The only reason people want to read a story is because it takes a common problem and makes it uncommon--or plants a common problem in a fantastic situation.

It soon becomes a question of not only what they want, but why they want it.

However, even after these two elements have been established, we're still left wanting more. We are just never satisfied, are we? Next, we want to know what will stand in their way? Unless there are hurdles and/or pitfalls along the road on which they're embarking upon, no reader in the world will care if they trip, get stabbed, or curl up in a dark hole.

Taking all of these factors into consideration, I have channeled my inner mathematician to devise a formula, which I think is quite reasonable.

(Their Wants + Their Reasons) + (The Challenges x The Antagonist) =

A *hopefully* Spicy Character on a Heroic Journey