Your first order of business is to choose a word which will be taboo to say at the party. “Halloween” is the obvious choice but you can pick any word you like as long as it is a word that is likely to come up in conversation often. For example “candy” or “costume” would both work very well.
Next decide on what you will use for the tokens. Classic wooden clothespins(you can decorate them if you like) work very as tokens since they are easy to remove and clip onto clothing without damaging the persons costume. You can also use safety pins, Mardi Gras style beads or anything else that is easy to remove and wear.
When you start the game give each guest one token and ask them to wear it. Tell them the taboo word and explain to them that the word is not to be said at all. If someone says the taboo word then the first person to call them out is to be given the token by the offender. Now one quick witted person has two tokens and the person who said the taboo word has none. The person with no tokens can get one back if they are the first to call out someone else who uses the taboo word.
This continues throughout the party until at some point near the end the person who has collected the most tokens is declared the winner and given a prize.