Should I use ellipses or two dashes to indicate a pause in speech? I had someone review my first draft and they told me that ellipses are to be used when speech trails off and is left unfinished, such as "I got hit on the head. I don't remember if he was wearing a hat, or..." he said, drifting off into thought. "Come on, you've got to remember or we won't catch the killer!" The reviewer also suggested that I use double dashes to indicate pauses in speech. "The last thing I remember seeing-- well, at least thought I saw-- was this ghostly figure coming at me." Here, the speaker is having a hard time sifting through memories and speaks hesitantly. My concern is that I don't recall ever seeing the use of double dashes in books I've read. When I write it into my dialogue, it appears to me as foreign, and I'm concerned the reader will stop and wonder about it each time, thinking it odd. I do seem to recall the use of ellipses to indicate pauses in speech, and it looks more natural to me on the screen/page, and fades into the text, much like verbal tags, such as "she said." "The last thing I remember seeing... well, at least thought I saw... was this ghostly figure coming at me."
I only use ellipses to indicate a sentence that never finishes the thought, such as your first example. However, if I were writing it, I would have nothing after closing the quote. "Drifting off into thought" is directing the reader a little too closely, but it also ruins the effect of the portrayal of the incomplete thought. As for a pause for a parenthetical thought, I think single dashes are appropriate. At least, that's what I use. Commas would also be appropriate: "The last thing I remember seeing, or at least thought I saw, was this ghostly figure coming at me."
I've never seen double dashes in literature. I think people mean you should type double dashes into your manuscript because, when it's printed, the printer will interpret that as an em-dash. Use double dashes when you want an em-dash, in other words. I agree with Ed about ellipses. Use an ellipsis when the thought isn't complete. You don't have to say "Drifting off into thought"; that's a bit redundant.
Em dash is definitely what would be used if you are looking for a dramatic pause in your writing or to tie in certain practical elements of the story. Ellipses is for trail offs; left out ideas. I agree with Ed and minstrel.
definitely not... see below... it's not a 'double dash'... a double hyphen is what's used in the ms to indicate you want an em dash to go there... the reason why the em dash is not used is that it's hard to tell a hyphen from a dash in many fonts, so the double hyphen makes it clear to the editor and printer that you want an em dash there... to show pauses/hesitations within dialog, only the ellipsis is accepted practice... an em dash is used at the end of a line of dialog, to show interrupted speech, the ellipsis for speech that trails off...
Interrupted speech: yes. Dramatic pausing: no. Interrupted speech: em dash. Dramatic pausing: ellipsis.