There is no one right way to make visualizations. These best practices are based on the research in the field of human-computer interaction. Sometimes rules are meant to be broken.
Choose a section to review:
The Colour section provides guidance on what colours to use, how many colours, cultural implications of colour, and some resource to help choose colours.
The Shape section provides guidance on how humans perceive shapes.
The Chart Elements section provides guidance on what elements will help your visualization accurately communicate the data.