Keep one source of data truth
Have one source of data truth for everybody on a project to use. Try not to allow people to copy their own versions of tables because it's easy for them to do some kind of manipulation that doesn't make it back to the main data source and makes their numbers different than everybody else's.
- Never update a column unless it has been well communicated to everybody. If you have a specific data need it is better to create a new column in the table than to update an existing column. This prevents somebody who was relying on the existing column from having unexpected results.