Creating grid to divide large map into smaller sections using ArcGIS for Desktop?

I have a map of small remnants of forest along creeks for an entire county in California. I need to divide the whole map into equal sections so I can print it so you can actually see the sections of forest. I'd like a map with a grid which I can look at, and then look at a zoomed in map of (for example) section A1.

I've tried the Grids and Graticules wizard, which gives me a grid for the map, but when I zoom, the grid remains the same. I want the grid sections to be georeferenced with the map, so when I zoom in, the grid zooms also.

I'm using ArcMap 10.1.