Graph Design

Components	Practices
Points	When sets of points cannot be clearly distinguished , correctly by: Enlarging the points Selecting objects that are more visually distinct . When point overlap such that some are obscured , correct by: Enlarging the graph and/or reducing the size of the points. Removing the fill colors.
Bars	Use horizontal bars when their categorical labels bars won't fit side by side. Never use horizontal bar for the time series value . Proximity Set the width of white space separating bars that are labeled along the axis equal to the width of the bars, plus or minus 50%. Do not include white space between bars that are differentiated by a legend. Do not overlap bars . Fill Avoid the use of fill pattern . Use fill colors that are clearly distinct . Use fill colors that are fairly balanced in intensity for the data sets that are equal in importance. Use fill colors that are more intense than the others to highlight particular things . Only place borders around bars when one of the two following conditions  exists : The fill color of the bars is not distinct against its background , in which case you can use a subtle border(e.g. grey). You wish to highlight one or more bars compared to the rest. Always start bars at a baseline of zero.
Lines	Distinguish lines using different hues whenever possible. Include points on lines only when values for the same point in time on different lines must be precisely  compared .
Boxes	Follow the principles for the bar design , except when box plots are connected with a line to show change through time , which might require greater distance between the boxes.
Combination	Use boxes and lines for the distribution through time . Use bars and lines in the form of the Pareto charts for the featuring the contribution of the largest portions of the whole . Use bar and points for the uncluttered comparisons.
Trends line	In most cases , use moving averages rather than straight lines of best fit to show the overall nature of change through time . Only use linear line in a scatter plot when the shape of the data is linear rather than curved .
Reference lines	Use references  line to mark meaningful threshold and regions, especially for the measures of the norm.
Annotations	Use text to feature and comment on the values directly when doing so is important to the story .
Log scales	Use log scales to reduce the visual difference between quantitative  data sets with significantly different values so they can be clearly displayed together. Use log scales to compare differences in a value as percentages .
Tick marks	Mute tick marks in comparison to the data objects . Use tick marks with quantitative scales but not with categorical scales , except in line graphs  when slightly more precision is needed. Aim for a balance between including so many tick marks that the scale looks cluttered and using so few that your readers have difficulty determining the values of data objects that fall between them . Avoid using tick marks to denote values at odd interval.
Grid Lines	Thin , light grid lines may be used in graphs for the following purposes : Ease look-up of values. Ease comparison of values Ease perception and comparison of localized patterns.
legends	Use legends for the categorical labels when the labels are not associated with a categorical scale along the an axis  and cannot be directly associated with the data objects . Place legends as close as possible to objects they label without interfering with other data . Render legends less prominent than the data objects they label. Use borders around legends only when necessary to separate legends from other information.
Axes	Don’t manipulate the aspect ratio to distort perception of the values
Data Regions	Keep the background clean and light.