We used to get a few but these days it's mostly the kids of people we know. We let them know when we'll be home and where to find us, and leave the porch lights off so we don't draw a crowd of others that we might not really want.
When we lived in the city it was really unpredictable. One year we'd have a load of kids coming round so we'd stock up on candy the next year and end up with three kids or something. It was nice to see the parents standing on the street keeping watch but letting the kids come to the door on their own.