Following CF conventions (source):

•  Title: what's in the file
•  History: Audit trail of processing operations
•  Description of the data
  •  units: units can be udunits strings e.g. 1, degC, Pa, mbar, W m-2, kg/m2/s, mm day^-1
  •  standard_name: Use CF standard names
  •  long_name: not standardised
  •  ancillary variables: a pointer to variables providing metadata about the individual data values e.g. standard error or data quality information
  •  * _FillValue, missing_value, valid_max, valid_min, valid_range
  •  Dimensions establish the index space of data variables
  •  Time (year, month, day, hour, minute, second) is encoded with units “time unit since reference time”

*Optional for numeric data variables

Embedded tags (tif tags):

•  Spatial extent
•  Temporal extent
•  Coordinate reference system
•  Resolution
•  No data value
•  Layers

For more documentation, create a README file.

Use a *.shp.xml to store the metadata in XML format (such as ISO 19115 or other XML schema):

•  Spatial extent
•  Temporal extent
•  Coordinate reference system
•  Attribute(s) meaning

Write in sheet/top lines of csv:

•  Title: what's in the file
•  Abstract
•  Measurement details