Every document that's been through a production cycle has the same problem: text that looks right on screen but is typographically wrong underneath.
The source is always the same. Someone pastes from Word. Someone pastes from an email. Someone copies from a website. The content is correct, but it arrives with the wrong characters.
The specific problems
Straight quotes are the most common. When text comes in from most word processors, websites, or plain text editors, the apostrophes and quotation marks are vertical straight lines: ' and ". InDesign expects curly quotes — the kind that open and close around words. Visually the difference is subtle. Typographically it's the difference between typeset text and typewritten text.
Em dashes are the second issue. The correct em dash character (—) is rarely typed directly. Most writers use a spaced hyphen ( - ) as a stand-in. And pasted text strips whatever auto-conversion the source application applied.
Double spaces are the third. Typists trained on manual typewriters learned to put two spaces after a period. Many still do. In typeset text, there should be one.
None of these errors will be flagged by any spell checker. They look plausible. They survive review. They survive preflight. They only get caught by a trained eye — or a GREP search.
The GREP approach
InDesign's Find/Change has a GREP mode that lets you search using regular expressions. This is the right tool for these problems.
The fix for straight quotes uses a lookbehind assertion to distinguish opening from closing: a quote preceded by a word character is almost certainly closing. A quote at the start of a word or after a space is opening. InDesign's GREP engine supports lookbehind, so this is a single find-change operation.
The problem is you need eight separate operations to cover the common cases: single open, single close, double open, double close, apostrophe in contractions, spaced hyphen, double spaces, and extra paragraph returns. Running them through the GUI one at a time takes five to ten minutes per document, and you'll miss one every third document.
Automating it
The One-Click Typography Janitor script runs all eight fixes in a single execution. If you have a text frame selected, it fixes just that story. Run with nothing selected and it fixes the whole document.
After running, it reports how many replacements were made. Useful for spotting documents that had heavy pasted content, and for confirming the script found what you expected.
Building the habit
The better long-term solution is catching this at the point of import. InDesign's Smart Text Reflow preferences include auto-quote conversion, but it only applies to text typed directly in InDesign. Pasted text bypasses it.
Running a typography cleanup pass on any text that comes in from outside your workflow is a habit worth building. It takes seconds with the right script, and it's the kind of detail that separates a professionally typeset document from one that just looks like it was.