How does one write P.S. (post scriptum) in Japanese?
Dictionary translates postscript as 追伸, but is that the compound one would use at the end of a Japanese letter or e-mail?
Yes, it is. Other variants are
The most common format is
at the very end of the letter after name and date.
When handwriting, it is common to indent further lines to match the start of the text, like so:
These are more style guidelines than rules as sawa points out in the comments below.
Adding to @ジョン's answer which I think it is the most general way,