There are many components to a good answer on Skeptics.
1. Void of speculation.
The primary purpose of Skeptics is to verify or falsify claims. As such, speculation is to be avoided at all costs as it unhelpful at verifying or falsifying anything. If an answer an be summed to "I don't know for sure, but here is what I think the answer is," then it is a bad answer.
2. References any significant claim.
At the present time, we have a strict "no original research" policy.
Simply put, hearsay and anecdotes are not enough. All significant claims have to be backed up by a reference that has credibility in the domain (i.e. no encyclopedia, no source which may be biased, etc.) and preferably peer-reviewed literature.
Obviously, not all claims have to be backed up. If the question can be answered with high school level science, no references are needed. The asker can always browse Wikipedia if is still skeptical.
3. Explains the methodology.
Citing studies is not enough. While a study may prove that X has a correlation with Y, the methodology is important - especially when it comes to social sciences where different definition of terms like "happiness" or generosity" would change the answer drastically.
4. Written in plain words.
Most Stack Exchange sites are intended for expert-to-expert exchange. Skeptics is different in that most users will be laymen in the topic discussed, be it biology, physics or psychology. For this reason, an answer should always be written in a plain language void of overly technical terms so that it might be understood my the average user.
5. Written in a polite and neutral tone.
As Robert Cartiano once said, "'[a] bunch of dicks' equals a failed site. It's really as simple as that."
We expect users to be respectful of others they disagree with, no matter how frustrated they may be. Rants about young earth creationists, "climate change denialists," etc. will not be tolerated here. If we want to introduce people to the evidence, we have to be nice. Otherwise, we'll drive them away before we even got a chance to educate them.