Graphical excellence consists of complex ideas communicated with clarity, precision, and efficiency.
Graphical excellence is that which gives the viewer the greatest number of ideas in the shortest time with the least ink in the smallest space.
Edward R. Tufte. The Visual Display of Quantitative Information. Graphics Press. 1983
Graphics should show large amounts of data; graphics should be dense. Exploit the resolving power of the eye and the pattern recognition of the brain. With bad design, the data can be obscured; but with good design, more than simple x-y relations can be shown.
Every drop of ink should be there to show the data. Axis ink can often be made to serve multiple purposes with clever design. Removing ink can often make the data more clearly visible. No more chartjunk, no more grid junk, no more fake perspective, no more garish colours -- just cool, clear, crisp graphics presenting masses of information.
Learning to graph with Excel is best accomplished with a trial and error approach. Let's experiment with Excel's graphing capabilities
Go to the Geological Survey of Japan's reference database at http://www.aist.go.jp/RIODB/geostand/welcome.html. Under the heading Recommended or preferable values, copy and paste some of the igneous rock chemical analyses into a new workbook. Clean them up and label them. Experiment with different ways to represent these data graphically. Here's a few suggestions to get you started.