- As a general query for the group to affirm that everyone is on board with the chosen course of action (or at least not loudly opposed). It's a way for me to check in and be sure everyone is going along with the plan.
- In situations where an individual is taking an action that doesn't sound sensible based on my perception of the situation. My intent here is to insure the player and I are on the same page. It may seem like this precedes something bad happening because if the player and the GM aren't on the same page, the odds of bad stuff go up significantly.
- In situations where an action has a binary state: either you do it or you don't. For example trying a weird key in a lock. It's an action that requires committing the key to the lock. No half measures, no cheesy "I did, but only half way" stuff. Once you do it there's no turning back.
Image courtesy of Colin_K: http://www.flickr.com/photos/22206521@N03