“One or two spaces after a period”
If it’s 1969 and you are taking a typing course on a manual typewriter, two spaces.
If you are using a modern word processor with proportional type, one space.
I think I got this from a book by Robert Parker, Looking Good in Print, but I haven’t read it for twenty years so I’m not sure I remember correctly.
Sister Victoria, in 1987, had special powers. She was the typing teacher and we used "electric typewriters." Of all the typing that went on in the class, not only could she hear when someone used the "correction" key and who did it, she could actually hear when you started a new sentence without double popping the space bar.
I swear it amazed me. She would call the student by name from her desk as we did timed practice assignments for grades. "Johnny, two spaces after the sentence! Beth, no corrections! Accuracy is part of the assignment."
So she was wrong and I've been doing this wrongly for 15 years?
See Poser’s #118 for why two spaces is incorrect 99+% of the time today.
Yep, I learned on a manual typewriter around 1964. It is difficult for me to shed that old training.