Take control of stacking order with Step and Repeat
The most common way to use the step and repeat command in InDesign is to create your first object in the upper-left corner, and then use Edit > Step and Repeat to create duplicates to the right or below the original item.
InDesign has a concept called "stacking order". This is obvious when objects overlap, but stacking order applies even when objects don't overlap. The rule is that the last object created is at the "top" of the stacking order. This becomes visible in InDesign CS5 when you flip open a layer in the Layers panel and see each object listed. The objects listed at the top of the layer are at the top of the stacking order.
Step and Repeat also follows stacking order rules. The last object created is at the top of the stacking order, so if you step and repeat to the right and down, the object in the last column and last row (the bottom right corner of the created objects) is on the top.
But what if you want the objects to be ordered the other way? What if you want the first object in the Layers panel to be the first object in your grid, the second object in the Layers panel to the the second object in your grid, and so on?
Easy. Just create the object in the lower-right of where you want the objects to appear, and then step and repeat with negative values to the upper-left corner. Now the upper left-object is at the top of the stacking order, and the bottom-right object is at the bottom of the stacking order.
Why would you care about this? When working with grid-based layouts, it might make more sense to have the objects in the Layers panel arranged from the top down. Also, when creating templates for certain XML or script-based workflows, the stacking order of objects is critically important.
To learn more about the new features of the Layers panel in CS5 and later, see this post.