I use a few for finding missing opening and closing quotes. They aren't perfect and I have to look at the matches before making changes.
Missing opening quote:
Code:
(<p>)([^“]*\”.*</p>)
With the replace:
Missing open quote between closes:
This doesn't have a replace string as I have to work out where the quote is missing. And in lot of cases, the wrong quote was used.
Missing closing quote:
Again, I have to work out where the missing quote should go. Or it it is needed when one persons dialog continues over multiple paragraphs.
These aren't perfect and I have to look at the matches before making changes.
There is a sticky thread in the Sigil forum with a lot of Regex example. It has a lot of good suggestions like this. I think the first one came from it.