Determine the purpose or objective of using the table. Typically this will be one or a combination of:
Providing an organizing framework for existing information.
Prompting for new information that is to be identified.
Presenting information in a clear and compact format.
Tables are easier to understand if they have a single unifying theme, although they can also be used to combine themes, for example a list of customer needs can have column sets on product features that satisfy those needs and also notes on how well competing products meet the needs.
Identify the general categories of what will be in rows and columns. For example, rows are products and columns are details about defects. The table will combine these categories to provide new information and help decision points to be identified.
Using the general categories from step 2, determine the exact rows and columns to use. For example, rows are 'products from line 3B' and columns are 'defect category, defect count and fix time'. When selecting rows and columns, beware of the table becoming too large, as this will make it less readable, particularly if it runs over more than one page.
It is common to put independent items (usually the 'primary' items) in rows and dependent items in columns. For example, the fertilizer to use will depend on the flower being grown, so a table of these would have flowers in rows and fertilizers in columns.
It is often practical to put the subject with the greatest number of items in rows, as there is usually less space available for columns. This is particularly true when the table contains text (as opposed to numbers or symbols), as this requires a reasonable column width.
Design the layout of the table such that the information that it contains will be easily usable. Wide tables may benefit from being drawn in landscape, rather than portrait format.
If the table is not completely clear, for example when using abbreviations to keep columns narrow, then add a key or instructional text to help its users and readers to understand it.
Write the information into the cells of the table. Be clear about the rules of how to select what does and does not go into each cell, and then use them consistently.
Interpret the completed table and take appropriate action.