Here’s a link to an old GQ thread on the issue.
In MS Word: <CTRL>-H, Find what: [two spaces], Replace with: [one space], Replace All. Repeat as needed.
I do this (among other style changes) with all MSS I get from other writers.
I’m with missbunny. Word doesn’t make the spacing after full-stops look right, not to my eyes, and I always double-space.
With fixed width fonts, the full stop itself creates the appearance of some extra space, so a single subsequent space can look fine.
Former newspaper journalist here. Always have done one space, as has every other journalist I have ever known. It helps you put more words to the column inch.
Monospaced font (e.g., Courier, Prestige): two spaces
Proportional font (most everything else): one space.
I had typing class in high school in the late 60’s. We used one space.
I never heard of two spaces until sometime within the last year. I figured it was some new-fangled internet phenomenon.
One space. None of my editors have ever insisted on two spaces, but some have insisted on one (saves a few pages of paper in the long run.)
Weird. I had typing class in high school in the late 70’s and we were taught two spaces. And that is what I use. I don’t recall if there was an explanation.
My computing teacher insisted I do it in 4th grade. So I did, and never stopped. Most places on the internet the two spaces become one, though.
RealityChuck is correct. I was taught in multiple college typography courses (late 80s) that two spaces follow a period in monospaced fonts, one space follows a period in proportional fonts.
That said, modern rules seem to favor a single space after the period in all cases, and the two space rule doesn’t have much of a purpose. Cite
Two-spacer, never used a typewriter. I have no idea where I learned this. I don’t think I’ve ever been told explicitly.
Even though much of the writing I do gets formatted to a single space after the period by whatever computer context it’s in, I still hit the space bar twice. Honestly I think it’s become sort of a mild mental crutch over the years, hitting the space bar twice helps my brain end one sentence and begin another. When I try and do it the other way it feels weird.
I took a touch typing class in high school in the 1950s. Two spaces for me forever. I couldn’t begin to change a fifty year habit. It’s just automatic.
Two spaces. That’s how I learned it in high school. Plus, I’m a medical transcriptionist who gets paid by the 65-character line, and spaces count as characters, so heck yeah, two spaces. 
I used to use two spaces - but that’s because our University essays were supposed to be “double spaced” and that’s what I thought they meant!! :smack:
Now I use one.
Grim
Interestingly, all the sentences viewable on this page are spaced apart with only a single space.
As previously mentioned, this is because of the way HTML ignores anything more than one space, or interprets a carriage return as a space, etc.
I do not find any of the lines written here to be hard to read because of this. Methinks modern technological-based typography has rendered dual-spaced sentence gaps as unnecessary.
And this is what DRIVES ME UP THE WALL about HTML, being a born-and-bred dyed-in-the-wool 2-spaces-or-die kinda guy. HTML has always looked UGLY no matter what to me (note the “to me”), and it’s because there’s not enough space between the damn sentences.
And don’t get me started on the fact that nothing conforms to the A4 size standard. Nothing bugs me more that a paragraph that takes up one line. 80 columns were good enough for my XT, hell, 40 columns on a IIe!
Ah, gimme a stylus and a clay tablet and a very big pigeon…
2 spaces, though, please?
I’ve always done two spaces after a full stop. I’m aware of the current preference for one, but I simply don’t think it is as readable, even with proportional fonts.
Technical writer here - commasense is right. On computers, one space, one space only. Learn it, live it, love it.
I always use two spaces at the end of a sentence. When I was learning to type I was told to do it that way, and I always do now I realise that some programs, like this board, will automatically drop it down to one space anyways, but I do find it makes things easier to read with that extra space in there. I don’t see any reason to train myself out of this habit especially if it is being automatically ‘corrected.’