Preparing and Using Visual Aids 219 Class Act Line charts are best when a variable has more than four or five data points and you want to emphasize continuity over several months or years. That's because the slope of the line tells viewers the direction of the trends at a glance. Is the chart easy to read? For example, have I labeled the x and y axes, lines, bars, or pie wedges? Have I made the most important text largest and the most important data lines or sections darkest? Is the chart accurate? Did I start a numerical axis at zero? Did I compare only like variables? Have I eliminated all unnecessary details? Did I avoid grid lines, data points, boxes, and other devices unless they relate to the message? Did I use no more than four colors per visual? Did I avoid distracting fill patterns, such as contrasting lines, wave patterns, and crisscrosses? Did I focus attention on key points by using color, shading, or symbols such as arrows? Did I write in upper and lower case to avoid the difficulty of reading words written in all capitals letters? Did I use presentation software sensibly? When necessary, did I adjust the default mode to simplify a visual?