About ten years ago an agent told me not to submit manuscripts in fonts other than Courier (or Courier New) and to double-space lines. He said editors were prejudiced against manuscripts that looked like they were written on a word processor (as opposed to a typewriter, I guess).
Assuming this was ever true, do editors still expect to see the monospace Courier font?
A significant proportion of agents and editors still want submissions in Standard Manuscript Format, which includes using a serif monospace font such as Courier. Many of them have become less fussy about the particular font and will also accept a proportional font such as Times Roman. However, in no case should you use a non-serif font, or anything that you wouldn't use in business correspondence. Double-spacing is still pretty much a universal requirement.
In general, you'll always be safe by sticking to the most conservative standard, as no one will be bothered by it, and some people still require it.
When I was doing work as an Editor I loved the Courier font, or any fixed pitch font for that matter. As nice as Times New Roman looks, after reading 100+ first pages it starts to wear on the eyes. A fixed pitch font just makes it easier to read page after page and in the end readability wins when it comes to formatting and fonts.
But as for what an editor expects. If they say they want it in Courier send it in as Courier (it goes back to the rule of Always Follow the Submission Guidelines).
When I edit MSS, I find it easy and natural to work on copy that's 'typed' in Courier and double spaced. Another fixed-pitch font might be OK, I guess, but Courier is by far the most familiar and the easiest to edit, AFAIAC.
It's impossible to edit matter set in a variable-spaced font;1 there's just not enough room2 to insert proofreaders' marks quickly and accurately.
So why not give an editor what she's used to? It can't hurt.
-- pete
1 Times is the worst, the total pits.
2 Because it's a virtue to set variable-spaced fonts tightly, in the least horizontal space. For example, try to correct the spelling of 'spellling' as it's set here. Can you even see the error?
First step: check the publisher's web site for their specific submission guidelines! They probably say right there how they want to receive your manuscript.
For reading purposes, stick to a good, well-known serif font (like Times New Roman), or slab serif font (like Courier). The reason I say this is because - regardless of your manuscript looking like it was written with a typewriter font - serif fonts are much easier to read in print than sans-serif fonts (like Arial).
On a writing course I've done, they gave the following recommendations as well:
Definitely stick with the double spacing of your lines. Use a new line for paragraphs rather than a spaced gap i.e. the spacing between the previous paragraph and the new one is the same as your line height. Indent each paragraph / new line, except the opening paragraph of the chapter/section.
I'd also recommend using single quotes for speech, rather than double quotes.
Edit: Note that these are likely UK-based styles, particularly the single quotes.
Courier Prime comes with a nice-looking italics character set. Italics are also monospace and look a lot like the old cursive typeface came with many typewriters back in the day. Thus, unlike most other versions of Courier, the italics are not just a slanted version of the regular font. It was written specifically for screenwriters and is available here, among other places. https://quoteunquoteapps.com/courierprime/
Any font with Courier in its name should meet the publisher requirement. Courier Prime has the largest character set and is available as a free download. My personal preference is Courier Screenplay, designed for Fade In software. It is pleasant to read and also available for free. Courier Final Draft, the default font in that software, is also a fine font and IIRC is also downloadable for free.
For readability purposes I recommend avoiding Courier New, the default monospace font in Microsoft Windows. The font was intended to emulate the familiar typeface used in IBM office typewriters, but the enhancing effect of typewriter ribbons was overlooked. Courier New characters thus appear too thin and are more difficult to read when printed on paper. (Windows was long ago patched to compensate for this on screen displays.)
