How to: Hang in a Grid

This weekend I did some rearranging and picture taking for an upcoming full reveal of Lilly's room over at hellobee.  The artwork on her walls hadn't been moved since she was in her crib and with her fab new bed and furniture arrangement, it was in need of some refreshing.
While we were in DC over the holidays, I went to the C. Wonder store at Tyson's Corner.  The line was out the door, but I found these faux bamboo rimmed plates and they were on sale.  I hastily grabbed all that they had, not really knowing what I wanted to do with them, but thinking they would be wonderful displayed on a wall.  I pulled them out this weekend and they ended up being the perfect polished addition to Lilly's big girl room.
I hung them in a grid over her bed and used my God-goven over thought and over complicated common sense, so you'll excuse me if there is a much easier way out there.  Here's the final product...

First, I laid the plates out on the ground to determine how I wanted to arrange them.  I decided on the three by three grid and had a couple plates to spare.

I then traced the plate outline on paper and cut out nine circles.  I attached the plate hangers to the plates and then laid one pink cut out over the plate hanger and marked roughly where the nail would go.  I used this one mark and marked all of the nine circles by overlaying them one at a time.  I made the marks dark enough so I could see them through the overlaid paper.  For this step, it is important to make sure you are using the same size plate hangers so you can make sure the nail hole is in roughly the same spot.

Using double sided tape I attached the cut out paper to the wall to determine where exactly I wanted them to hang.  I eyeballed this step and didn't worry about being too exact.

Once I found a good spot for the middle plate, I used it as a guide.  The nail hole I marked on the center paper was used for the spacing of the rest of the plates.  

Using a level and the nail hole on the center plate, I drew a faint level line (on the cutouts) connecting the nail holes on the middle row of plates.

I then did the same thing with the level and drew a line for the middle column.  The + made on the center plate became my more exact guideline.  I then determined the exact spacing I wanted by moving the plates around until I found a distance I liked.  Once I did, I measured the distance between the marking on the center plate and the one just left of center.  I marked this number on my ruler and used this same number to mark the rest of the nail holes, using center as a guide.  It doesn't matter what this number is, as long as you use it through out.  You will probably end up making new nail hole marks on all of the plates.  The most important part is that the nails are evenly spaced.  As long as the nails are the same distance apart from top to bottom and left to right, you will have a lovely grid.