The visuals are the most important part of a dashboard. You can usually do without the numbers or hide them in drilldowns or rollovers. You can almost always remove tabular data.
People comprehend information by using comparison and finding patterns. For example, use a red diamond to draw attention to issues. Things that are good or neutral can usually be left unadorned since only the bad events are what really matters. If everything is color coded green, yellow, red, the red does not stand out. If you only color the bad things red and leave the others as grey then it is really easy to spot problems from afar.
"Dashboards are for monitoring! Let me know if there are any problems, otherwise I'm going to go back to work."
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