One trick I've found in Word specifically: press Ctrl+v to paste, then hit Ctrl, then hit 't' -- this is the key sequence for paste->open paste options->use pla

One trick I've found in Word specifically: press Ctrl+v to paste, then hit Ctrl, then hit 't' -- this is the key sequence for paste->open paste options->use plaintext. You can do the same thing by pasting, then click on the little box that pops up next to your pasted text, then clicking the text option.