When using the Sense Motive skill to determine if a character is under an enchantment, do PCs have to declare they are observing a character for suspicious behavior indicative of being enchanted or do they get one automatically?
In the past, I have given this check automatically; however, after reading it again just now I can't see anything by RAW either way.
There'd have to be some degree of interaction before any such check, but given the limits of the medium (that is: the GM's narration versus actual person-to-person interaction) I'd say it has to be granted automatically.