Chart Clutter
Busy Graph
Data Focused Graph
Make sure the focus of your visualization is the part that represents the data. There is a lot of debate on "chart clutter" as it can distract from the data, but helps the viewer remember and stay interested. A good rule of thumb is just to make sure that the data portion is the primary focus.
Labels
Hard to Read Labeling
Easy to Read Labeling
Labeling on Your visualization should be easy to read.
Start the Axis labels at 0
Y-axis Does Not Start at 0
Y-axis Starts at 0
Starting a numerical axis above 0 can distort the representation of the data. In the example above, the first chart makes it look like the "Other Team" has half as much value as "Our Team". The Chart with the axis starting at 0 illustrated that that is not the case at all. Sometimes you need to start the axis above 0 due to the scale of the data. In this case, make it clear with labeling/ text that it does not start with 0.