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.