Possible tells for correct answers: nodding, smiling, writing the response on the board, not asking for additional responses, verbal cues like "good," and asking for an explanation. Possible tells for incorrect answers: moving head to the side, slightly shaking head, not writing the response on the board, verbal cues like "maybe" or "interesting," and asking for an explanation. I think tells really depend on the person. A tell for a correct answer from one teacher could be a tell for an incorrect answer from another teacher.
Responses to wrong answers that might help to build a Culture of Error: "I love how carefully you thought about this problem. Let's take a look at some possible changes." "This is a tough question, so I expect we'll have a lot of diverse discussion about the answer." "Don't worry about getting the right answer here. Focus on the process and be ready to justify your response."
If students are rounding 246.74 to the nearest hundreds place, they will likely make errors by rounding to any other place. Instead of the hundreds place, students might round to the hundredths place, or the ones place, the tens place, etc. To address those misunderstandings, an instructor might ask other students in the class to explain how an answer of 247 is indeed rounding, but which place are we looking at? How do we know which place is the hundreds place?
A question that might need deep excavation: "Why is it important to cite your sources?" a. Potential wrong answers: "It's part of the assignment requirements," "Our teacher needs to see where we're getting our information," "Our teacher wants to make sure we're not plagiarizing," etc. b. Although the above answers are not completely wrong, there's definitely a better answer to a question of why it's important for students to cite sources. Students often think teachers ask them to cite sources as a way to make sure they're not "cheating," Instead, it might be helpful to have a conversation about healthy and ethical scholarly contribution. We ask students to cite sources so they can build upon an ongoing academic discussion. We're training them to make their own contributions after they have carefully reviewed what other experts have already said in regards to a particular topic. It's a way of making sure they're informed and ready to add something new.