Quote Originally Posted by ad_hoc View Post
An easy way to check most rulings is to flip them around.

Take a situation where the party were talking to some creatures and the creatures suddenly attacked. The DM then declared that the characters were surprised. How would the players react?

The players would likely be upset. It would also create a situation where the players proclaim they attack whatever they see as soon as they see it so they don't get surprised.
Yup.

Personally, my adjudicating surprise situations is strict:
- Unless there's an intentionally attempted ambush planned in advance by one side, and a clear case of the other side not expecting any danger, surprise automatically does not happen.
- If both of those are true, then surprise must be rolled for. The roll involved may be a variant from the usual Stealth vs Passive Perception, including involving adv or disadv or group checks etc, at my discretion.
- Attempting to surprise can never be automatically successful.