Define a data dictionary early in the project to efficiently describe and document your data.
Data files and data descriptions should be well-organized, managed, and documented to ensure that files can be located and their contents are understandable.
How to describe the contents of a data file
How to describe the units of measurements for each observation
One should be consistent in the types of data included in columns of spreadsheets or data tables.
Keep descriptions and flags for data separate from values
Understand the geospatial parameters (resolution, reprojection, datum, scale) of spatially-referenced data when integrating geospatial datasets from multiple sources.