These words should be used sparingly and individually. After each word use, time should be taken to check upon the effect of said word, on the weasel, or weasels. If no effect is witnessed by the word sayer, it is an indication that the word was: pronounced incorrectly, spoken in a tone that the weasel approved of, or was simply a duff word.
If you are with company, it is worth allowing your friend/partner to use the word after you; this will guarantee that it was in fact, a duff word, and not just a miss-speaking.*
*Never repeat a word yourself, as this may well cause an attack mechanism in the weasel, which may result in loss of life/lives/lifes/lifs.