What are the "rules" for Trick or Treat? Well, parents take the little kids around, often in groups. Older kids go by themselves. When I was a child, we sometimes got homemade treats, like cookies, or little boxes of raisins, or apples. No more--not since some crazy people gave out apples with razor blades in them! Now, candy must be commercially wrapped. Some people prefer to give pencils or stickers, but most people give candy.
If you think that children will be trick-or-treating on your street, you can buy inexpensive candy by the bagful at any supermarket. Give each child a handful of small candies or 2-3 little chocolate bars. Be sure to get something you will want to eat yourself, in case there are leftovers!
The children usually start trick-or-treating around nightfall; the exact time depends on the neighborhood, but usually 6:30 or 7 p.m. If you want trick-or-treaters, turn on your outside light, and maybe, leave your door open (if it's safe). You might want to put a pumpkin (or a carved jack-o'-lantern) in front of your door, or hang some Halloween decorations (ghosts, goblins, witches, and jack o' lanterns are all traditional) to make your place look more inviting. (If you don't want trick-or-treaters, keep your door closed and your light out; that should discourage them.)
If you live in a neighborhood without many children, you are not likely to get trick-or-treaters no matter what you do.
If little kids come to your door, you should compliment them on their costumes or ask them what they are (a ghost? a princess? a witch? a Teenage Mutant Ninja Turtle?). They will say, "Trick or treat!" That means that if you don't give them candy, they will play a trick on you. But don't worry: if you opened your door to them, you probably have candy to give them.
When you run out of candy, turn out your light; Halloween is over until next year.