With more and more stories like this popping up in the past few years, GEB reader "Will from the UK" has built a slick tool to help with the process.
In his words:
I enjoyed your post about the archaeologist who found interesting artifacts in Saudi Arabia using Google Earth. It got me thinking about how to do a systematic search of an area using GE.
There are no tools in GE that help, other than the usual lines / placemarks. Marking an area out using lines is fairly tedious. A grid is a useful solution. I have seen grid generators online, but they tend to come and go, and you need to be online to use them.
I have created a spreadsheet that generates the KML code for a Latitude / Longitude grid. A grid allows a more systematic search to be conducted and also allows more people to take part in a search - the work can be divided between many volunteer searchers.
The resulting spreadsheet is quite impressive, and it is a great way to divide up a large area for more precise searches.
You can download the Excel-based spreadsheet here. The spreadsheet is remarkably powerful, though it has a bit of a learning curve and a few limitations. Fortunately, Will has been generous enough to develop a User Guide (PDF) to help you get started.