How do you trick or treat in America if you're foreign?

If your foreign and are not sure what to do on Halloween just read closely.First off to give you a bit of back round on what it "WAS" used to do.It was used to scare off evil spirits back in the 1700's or so i'm not completly sure when i just know that much.Now for what you will be doing on the day for you is first walk up to the door and sometimes they'll be sitting on their porch waiting for trick or treating people.You either nicely knock on their door and wait for an answer if no answer then just go to the next house to it.Don't feel like you arnt going to the right house because on Halloween ANY house is the right house.Now if their on there porch just say "Trick or treat" and they'll say "pick one" or just hand you some candy then say "Thank you".You can really dress up at anything at all don't think either it has to be scary or gore filled if can be nice funny and what ever you like. I'm sorry this is such a log response but i just want you or someone that your with to feel right at home on one of America's finest Holiday's