D.W. explains what to ask. Here are some pointer towards how.
Wait, first the when:
First, talk to people, namely fellow students, TAs and teachers (in that order). Many problems go away after you talk to somebody who is thinking about the same problem, or has done so before.
If that is no option (really?) or does not work out: Google your problem. ...
Ask questions about concepts, not about your exercise
Don't ask us about how to solve your homework exercise. Instead, spend some time trying to solve the homework exercise, and use that to figure out where you have a conceptual gap in your understanding.
Then, ask about the concept you don't quite understand yet.
If you've done a good job of this, often ...
The original proposal seemed to be to hold the AMA itself on meta, which isn't what meta is for. If there is an AMA, it should be on chat.
I also note that the AMA on Physics seems to have run monthly but then had a hiatus of several months. Physics is a rather larger community than ours (they have 133 users who've earnt 100+ reputation so far this month; ...
Interesting proposal, but I don't think an AMA is the best format for this site. The 'M' part is the part that I think doesn't really fit, why should the focus be on only one person? Couldn't other experts also have good or even better answers to your questions? If you want to know something related to that person in particular, you can simply use the chat ...
The general rule is: don't edit questions in a way that would invalidate answers that were correct at the time.
If all existing answers are incorrect or incomplete, we get into a gray area. On the one hand, we don't want to flood the site with duplicate questions just because they didn't get a good answer the first time round. On the other hand, if your ...
Treat it as you would any other question based on a document such as a paper, blog post or somebody else's question or answer.
Link to the document you're talking about. The natural way to do this will be something like "In my answer to this question, ..."
Include enough context in the question to allow somebody to understand the question without having to ...
It took me a while to figure out why you thought this sentence had any purpose. Oh, you wanted a better solution than the answer you'd posted? As a general principle, your question should stand on its own: refering to an answer doesn't make sense. In any case, it's obvious that you'd be looking for the best answer (for some value of best that you neglected ...
Algorithms are generally on-topic; implementing them is a gray area since programming questions are offtopic.
This question would certainly be welcome on our site.
Note that we have a tag [distributed-systems] with many questions on Paxos already.
A word of warning
If what you are working on has been assigned to you for homework, asking about it on the internet may defeat the purpose of the exercise.
If your teachers know what they are doing¹, assigned exercises will encourage you to
review the requisite material,
work with the definitions and theorems²,
connect different concepts,