Using GPS coordinates provided on this site
Every set of directions provided on this web site was initially mapped out on Google Earth, then driven at least once by yours truly. In some cases, a better or more interesting route was discovered while actually driving in the area. Finally, the mileage, GPS checkpoints and navigational notes taken during my trip were checked on Google Earth again before the final version was written up. I have given great effort to ensure that these areas can be accessed using the odometer references or the GPS coordinates. Ideally, you should take advantage of both.
I always begin my trips by entering a herd area's GPS coordinates into my satellite navigation unit. More often than not, the unit maps out an unnecessarily circuitous route, betraying an obvious preference for pavement and named roads. If you use a sat-nav unit, I highly recommend keying in a few checkpoints before leaving on any of these adventures -- but don't be surprised when my described route strays from your sat-nav's. If you happen to miss a turn, or a road proves impassable for some reason, you can always default to your navigational unit for an alternative route.
My personal opinion on these devices is that they are great for finding a quick route to places in the civilized world, not so much for locations off the asphalt grid. However, they are fantastic for ensuring that you will always find your way back out of the wilderness, once you're there. If you don't own one, consider investing in a reasonably-priced window or dash-mounted unit. And please -- PLEASE!!! -- follow the written directions provided for these herd areas very carefully!