Choosing the right chart type depends on what you're trying to show: a line chart suits a trend over time, like monthly revenue; a bar chart suits comparing categories, like sales by region; and a pie chart suits showing parts of a whole but only works well with a small number of categories, since more than five or six slices becomes hard to read. Both Excel and Google Sheets can generate a chart from a selected data range in a few clicks, then let you customize titles, axis labels, colors, and legends. Common mistakes include using a pie chart for data that doesn't represent parts of a whole, starting a bar chart's axis at a number other than zero (which visually exaggerates differences), and cramming too many data series onto one chart until it becomes unreadable.