LONDON (AP) — Trick-or-treaters beware: Manners count — even on Halloween.

Britain's authority on etiquette, Debrett's, issued its first guidance on Wednesday on how to behave during the uber-American holiday.

Although the holiday originated with Europe's Celtic pagans to mark the end of summer — typically celebrated by bonfires to ward off evil spirits and children disguised as spirits of the underworld — it has only been recently that British stores have swelled with Halloween stock and trick-or-treaters have canvassed streets for candy.

"Good manners are very important," said Jo Bryant, etiquette adviser for Debrett's. "There has been a growing presence of Halloween over the past five years and we're receiving many more queries on how to behave."

Common questions are: Is it acceptable not to open one's doors to trick-or-treaters? How many times should children be allowed to ring a door bell before moving on? And can one forego a Halloween costume at a party?

Debrett's has posted its advice to the etiquette-challenged on its Web site.

"Trick-or-treat should be used as an ice-breaking formula, not a real threat. Halloween fun should never feel menacing," it says. "Children should not be too greedy — if they are offered treats, make sure that they don't take too many and that they do say thank you."

Other advice includes respecting people's privacy — don't repeatedly ring door bells for candy — and if you really don't want to be bothered by trick-or-treaters, it is perfectly acceptable to leave a bowl of treats at your doorsteps so children can help themselves.

"In this day and age, people have safety concerns and there is also a feeling that trick-or-treating can be intrusive," Bryant said.

Debrett's began in the late 18th century as a guide to England's aristocracy.