Here's what readers want in their characters:
1. someone they like
2. someone with courage
3. someone they understand
4. someone who makes things happen
5. someone tenacious
6. someone passionate.
In other words, readers like to see characters who are an idealization of their own dreams. You know that moment when you walk away from a bad conversation and rethink it with great comebacks and snappy lines? Readers love to see their characters find those great comebacks and snappy lines.
But not all the time! A great character has to fail, too, and fail miserably. A great character (protagonist) needs a great obstacle (antagonist) to fight. In fact, that obstacle has to be huge - life and death.
Now, to a 10-year old, life and death may be her parents' divorce. Or it may be experiencing supreme embarrassment. A comic life and death moment is a twist on the serious - showing up at a non-costume party wearing a costume.
When we writers create characters, we have to think about them within the framework of the obstacle they face. And give them a desire so important that it motivates them to act.
So, it's character to desire to goal, all blocked by the big obstacle.
How do I, personally, tackle this?
Well, usually my stories start with an abstract idea. In other words, my plot comes first. But almost at the same time I envision the character who will deal with this idea. Often I free write a number of scenes, getting the emotional tenor and voice of the story rolling in my head before I write the story itself.
But before I write much of the story I try to get to know the character, by one or more of the techniques I've already described. This is just the "getting-to-know-you" phase of writing. It usually isn't until I've written most of a complete first draft that I feel I really know my character.
Then I'll go back and do another round of character studies! I might re-web, or interview my character, or make another scrapbook, or write a series of pages of character backstory.
This is a very organic way of working, and that's what works for me at least through the third draft. By that time, if my character isn't fully developed, the story probably isn't working, either.
And, by the way, I probably end up with between 15 and 20 drafts (or more) of a single novel/story. But more about that stage in another post.