Lerwick doesn't really have that many triggers. The only two he really has are the doorbell, and the vacuum. The vacuum trigger came on slowly. At first, he just ran away from the vacuum when we used it. Then he started barking at it from a distance. Then he started barking and play-bowing at it and trying to bite the cord. We began crating him whenever we wanted to vacuum.
Interestingly, he taught himself a coping mechanism for the vacuum. One time when I was just going to vacuum up a small spill, I decided it wasn't worth the hassle to crate him. Of course, as soon as I turned the vacuum on, Lerwick started barking and circling. However, as it happened, right beside the vacuum was one of his toys. Lerwick grabbed the toy and started running around the room, brandishing the toy at the vacuum. So now, that's what we do. We leave one of his toys out near the vacuum when we start it up, and every once in awhile toss it or play tug with him for a moment while we're vacuuming. He still gets to "play" with the vacuum, but not by barking and biting at it.