Visible crew/equipment: When Riley goes to Spike's crypt to ask him for information about Dracula, the microphone appears in the upper right hand corner of the screen. (00:17:55)
Visible crew/equipment: When Willow and Tara are talking about Dawn, just as Willow turns around from hanging her picture to say "help?", a boom mike drops in from the top of the screen. (00:18:35)
Visible crew/equipment: When Harmony sits down opposite the operating table, behind her in the glass there is a reflection of a boom mike.
Visible crew/equipment: In the final scene where Buffy apologizes to Dawn, a microphone is visible in the upper left corner, from the camera angle behind Dawn, just after she says "you hurt my arm." (00:40:00)
Visible crew/equipment: In the scene where the demons are attacking, one of the demons throws Buffy across a table. If you look carefully, you'll see the black mat which softens the stunt double's fall on the floor when she hits the ground.
Visible crew/equipment: When Spike picks up the money after Buffy has just said "you're beneath me", you can see the microphone "sender" under his leather jacket. (00:36:10)
Visible crew/equipment: When Giles picks Buffy up in his car, you can see lighting and camera equipment on the right.
Visible crew/equipment: In the episode "Into The Woods" at the very end you see shots of Buffy and Riley from both the helicopter and the ground. The 2nd shot of the helicopter you can see a camera in the top right corner of the chopper. (00:40:35)
Visible crew/equipment: In the final scene in the Magic Box where Buffy cries, in several shots of Buffy you can see, in the right of the shot, the sleeve of a white shirt, which none of the characters are wearing.
I Was Made To Love You - S5-E15
Visible crew/equipment: As Warren talks on the phone with Katrina, in the mirror above the fireplace behind him, you can see the reflection of the boom mic following him around as he moves.
Visible crew/equipment: After Buffy walks outside to hear the sirens, in the close up of Buffy's face on the upper right corner of the screen you can see a boom mike. (00:06:30)
Visible crew/equipment: Buffy and the gang are in the waiting room after being told the cause of Joyce's death. After Willow asks "Why don't we sit down?" the camera pans from right to left and the camera focused on Dawn becomes visible at screen left. Some frames later it appears again as Dawn leaves to "pee" and the camera zooms out. (00:32:55)
Visible crew/equipment: When Tara says "take care, Dawn" and the shot changes All The Way to the left, you can see a crew member just sitting there.
Visible crew/equipment: When Buffy is sitting on her bed, you can see the edge of the set at the top of the screen.
Visible crew/equipment: When the knights start advancing in the bottom right corner of the screen you can see a crew member wearing a red plaid shirt just standing there.
Visible crew/equipment: When Ben arrives in his car and discovers the Knights of Byzantium, the shadow of a camera on a crane can be seen in the bottom left corner of the screen as he pulls up.
Visible crew/equipment: When Willow does her spell to save Tara, you can see the black pad Tara falls/ stands on.
Chosen answer: From what we see in the series, certain girls are identifiable as potential Slayers - Kendra clearly fell into this category. The identification method is presumably mystical in nature, but the Watchers' Council are pretty effective at that sort of thing, so they're quite good at tracking down the potentials ahead of time. Not perfect, though - it does appear that Buffy herself may have slipped through the net - certainly she had no inkling of what she was until she'd already taken on the role of Slayer. It is possible, however, that this was actually cultural - an American family would hardly be likely to turn over their daughter to some strange man for 'training', so the Watchers might have chosen to keep an eye on her covertly, whereas some other cultures (like Kendra's Jamaican parents) might be more willing to believe.
Tailkinker ★