Avoid duplication

If something is written once and you can easily link to it, use the link. Duplicate content produces poor search results, confuses the user, and it can be hard to catch and update all of it.

If users can find two similar yet slightly different pieces of content they will stop what they are doing and ask for guidance. Worse, if the user can't decide between multiple search results of similar content they may pick the wrong content.

Consolidate. Direct the reader to the right location — ask someone if you aren't sure.

Before you start writing, check to see it hasn't already been written.