The hardest nits to find are the invisible ones, and for that purpose ‘Find and Replace’ is a potent tool in some respects. The simple premise is that, to remove double spaces, for example, we ‘find’ them all and ‘replace’ them all with one space in a single action.
Of course, we have to run this process more than once to eradicate multiple spaces.
But Find and Replace is also great for removing hanging spaces between periods and paragraph returns, and, more importantly, hanging spaces at the beginning of paragraphs because they will not line up with other paragraphs, should any spaces exist.
Here is a paragraph with all of these nits, but they are tough to spot: