Closet Design

I've started working on clearing out the room that will soon become our nursery.  Unfortunately, the current closet organization leaves much to be desired.  I am in the process of removing the existing boards and once I patch and paint the walls, I want to install new wired shelving from Rubbermaid. 

However, I can't decide what would be practical for a child's room.  I know I need to be able to hang up clothes, but should there be one bar or two?  How many shelves should I install for toy and diaper storage?

I should mention that it is a walk-in closet.

Here's a terrible collage I made in Picasa:

 

Here's what I had originally.  There were hooks along the left wall and a small shelf along the right wall.  These walls measure 5'8".  You can catch a glimpse of the previous bar in the middle of the photos.  That is the wall opposite the door and measures 4'.  The ceiling also has a slope, so doing two tiers of clothing there isn't exactly practical.  I could do the clothes along the left wall and a few shelves along the back wall.  That would allow for plenty of storage as well as space to walk in the closet.  

For those of you who are already parents, what are your organization and storage secrets?