In a bit more detail, you can make a dashboard glanceable by following these guidelines:
Ensure that there is clear purpose in your metric design and display. In other words, think about which metrics you want to show, how you want to show them, and where you put metrics in relation to one another.
Group metrics by function into sections. Look at the dashboard above. It has four clusters of metrics: those around revenue, new customers, revenue per customer, and customer acquisition cost. All of the revenue metrics are clustered in the top-left quadrant of the dashboard. Furthermore, all revenue-related metrics (that is, revenue metrics and revenue per customer metrics) are on the left-hand side of the dashboard, so the CEO can focus on that half and learn about revenue and revenue per customer. She doesn’t need to look in the top-left corner for one revenue measure and in the bottom right for another; she can focus down to a portion of the dashboard and get an answer.
It should be easy to see and differentiate those clusters of metrics. Our natural instinct might be to put borders around the clusters, but whitespace is your friend—remember, less is more. If you add a bit more whitespace between clusters of measures, you’ll make it easy for people to see that there’s a difference without distracting them with unnecessary lines.
I cover the Rule of Thirds, Glanceability, and Color Vision Deficiency, three important considerations for a designer.