in olden timey days, they taught more or less like this: hyphenate between syllables, in general, more than half the word should be on the first line. If the bell has gone off, then generally don’t start a long word. After the bell, there is room for 7, or 6 plus a hyphen. If your word is longer than that, save it for the next line. Use the margin release sparingly. For example, you might need a comma after the last word. ,
via u/LycO-145b2 at https://reddit.com/r/typewriters/comments/1m2vc8m/rules_for_endofline_hyphens/n3soefg/