Keep It Simple
Avoid adding too many data points to the chart, as this will compromise its readability. For example, while the chart can handle easily hundreds of thousands of data points, plotting such a dataset will most likely result in a point cloud. Consider using sampling or clustering techniques to reduce the number of visible data points.
Use Consistent Colors
If a fourth dimension of data is not required, you can use colors that have sufficient contrast from the chart background - for example darker colors on a white background or vice versa. You should also avoid close colors if you plot different data sets as this can also compromise legibility.
Choose Correct Axis Scale
For datasets with values that differ drastically in magnitude, consider using a logarithmic scale to present the data more concisely.