Scare them Smart
I choose to scare the second passer-by first, I do them, move to a new location and scare the first person . The first scared second person's screams didnot give away anything (Usually) because it is over with and vanished before the number one customer in the lead can even turn around to see what may have scared the second person. Hearing and sort of seeing the person right behind them ,may just set the First person up more too? Anticipation builds for the unknown scary thing lurking.. somewhere.
One bright, sunny Sunday afternoon I managed to get a good scare from maybe 15 of 18 adult "Bikers", one at a time, as they walked into my "Tomb". I was standing behind the tomb door and as they would peer into the darkness at the other end of the tomb(Which is surprisingly long!) I would reach at them with my home-made "Clawed hand from between the door's
edge on the higed side!