If you are jumping into a question that someone is already answering, be aware of that. Offer assistance but try not to talk over each other as multiple answers and differing advice can be overwhelming.
Try not to hijack another student's question. if you are having a similar problem, feel free to jump into the question, but if you find you actually have a different question, open your own question to the community.
Rather than just trying to help students solve their error, try and help them understand the tools they need to solve the error. We think the best way to help students learn is by using the Socratic Method. This is a way of answering some one's questions by asking them questions. It may sound confusing but this will help a student better learn how to solve the error on their own next time!