Think of the MSDN forums as a gigantic FAQ generating discussion system.  The question and answer tags within threads enable users to easily see what threads contain answers and what posts within that thread actually provided the answer to the question. 

The answer tag is also used to improve a posts ranking in search results for end users.  Think about the end VS user searching for an answer when deciding whether or not to use the “mark as answer” button on a reply. 

Our goals define a healthy forum as one where 80% of the threads contain answers and that the average time to answer is three or less days.  The ideal scenario involves user one asking a question, user two posting a reply that answers it, user one reading the reply, and user one giving credit to user two by marking that reply as an answer to his or her question. 

We do what we can to encourage the askers to mark replies to questions as answers, but if they have decided to take the answer and run there exists the answer tagging role that can be employed by a large number of people including MS Employees, MVPs, Moderators, and top answerers. 

When to Tag Answers
Answer taggers should be aggressive while educating the community about the practice. Our experience so far shows that the answer tag does not kill off the conversation, but does help answerers focus their attention on users that still need help. 

Please tag replies as answers in the following situations.

1. If you asked the question: If you asked the question and a reply you received solves your problem you should use the “mark as answer” button you see on the reply to give the answerer credit for helping you out. 
2. If you are confident in a reply as the answer: If you posted a reply or you see a reply that you are confident answered the question. Remember that the person who asked the question can always “unmark” a reply as an answer to re-open the question if you were wrong. 
3. If a reply adds to an existing answer:  Remember that multiple posts in a thread can be tagged as an answer if they provide additional useful information. If there is a second, third, or more replies that add value to the original answer you should increase their weights in search results by attributing these replies as answers as well.

When Not to Tag Answers or When to “UnMark” Replies as Answers
If you have the answer tagging role or are the person who asked the question you have the ability to remove the answer tag by using the “unmark reply as answer” command. 

Please use this if:
1. You don’t consider the issue closed: It may be valid to redirect someone to another resource, but if a reply is tagged as an answer that does not answer the question you should unmark it in order to keep the issue open because you believe there should be better replies.
2. The answer doesn’t add value: This is probably the same as the first, but keep in mind that answers are bubbled up to users in search results. If you feel that you would not be helped by that reply if you came across it by searching then it should probably not have received the answer tag. 

This is the first of a few posts I’m going to do after having been the primary driver of the MSDN forums for a while in order to gather feedback on our moderation guidelines.  Leave feedback if you have additional thoughts or suggestions.