The Map helps new and experienced DMs quickly describe a dungeon, lay out a town, or, in some cases, set up a temporal flowchart of actions and events. And the chief tool for setting any of these up is graph paper.
Now graph paper is readily available in office supply stores and most retail stores. At 4 squares per inch, a single 8.5" x 11" sheet of typical graph paper yields 34 x 44 squares, which at 5ft per square (the de facto scale of modern maps) ends up being over 37,000 square feet of area to map. For most maps, this should be more than enough area, but what if you need something else? Maybe you want more area for a larger map, or to detail a major city, or what if you're like me, and you want extra area around the map to add all sorts of notes and legends? Then you might want to check out some of the links below.
Recently, while looking for non-standard graph paper, I came across a couple of great sites featuring more graph papers than I could have imagined... and they are all free!
The first site I came across, stitchpoint.com is a needlepoint/cross stitch site with a nice select of graph paper templates from 5 square/in up to 20/in, all in PDF format. Here's the direct link to their graph paper page.
printablepaper.net. They also have the same sizes of grid paper as stitchpoint.com. Just looking through all the options is starting to spark new ideas, such as the timeline paper for detailing a world history, to the hex and octagon papers for creating flowcharts, and just like stitchpoint, all the templates are free and in PDF format.
So remember, make sure you have access to the right tools for the right job, and the case of being a DM, that sometimes means the right paper for the right map.