Map Drawing Tutorial 15 (Part 1): Isometric Mapping
A lot of people use formal grids when they draw up isometric or perspective maps. You may note that drawing maps "the Vulpinoid way" doesn't use proper grid paper at all (there will be another tutorial addendum coming soon with some ideas along these lines). For this style of map, we draw a basic grid with pencil to get the placement of buildings basically right...then we basically ignore it, and erase it at the end of the drawing process.
An isometric or perspective map can be used to give players a better sense of place, sometimes providing details that a flat plan simply can't portray, sometimes adding elements of depth in a more meaningful way that spatially-challenged players might have problems visualising, and other times just because it looks cool. This style of mapping really starts to blur the line between cartography and scenic illustration.