http://www.reddit.com/r/movies/comments/1on3pz/keanu_reeves_ama_oct_20_2pm_edt_in_riama/

How do these AMA's work? Like a chat or something?

ANI!!!!!!! you've got to be online for this. !

what do I even ask

"What's the deal with white tablecloths, really?"

"Which of your characters would you most want to hang out with?"

"Are you absolutely certain that your spleen is still in you?"

"did you ever get the note i wrote on a napkin and slid under your door"

is it like a million people talking at once? I'm assuming you need an account to participate but do you have to do anything else in order to participate?

never used reddit before.

is he just going to wait for people to ask him random stuff or is he there to talk about a certain thing??

It would suck for a convo with someone you admire to be boring!

If other people in the community think your question/post is good, they'll upvote it by clicking that upwards arrow sign next to the post. The more upvotes (=points) a post gets, the higher up it rises in the queue (older posts will otherwise get buried by new ones), hence the more likely it is that it'll be noticed and hopefully answered.

Celebs will start off with a brief intro post. Sometimes they promote stuff in it (like a movie; people said that Keanu might be using it as a chance to promote 47 Ronin and Man of Tai Chi), but they might also answer all sorts of random stuff, depending on their mood.

Here's a recent one that Benedict Cumberbatch (Sherlock, Star Trek) did, to get some idea:

http://www.reddit.com/r/IAmA/comments/1o8l5f/i_am_benedict_cumberbatch_ama/

(click 'load more comments' to see replies to each post; as you can see from there, posts that BC replied to got a lot of points so as to push them to the top.)

Reddit AMA FAQ is here; particularly, the voting etiquette section shows the kind of things people should ask:
http://www.reddit.com/r/IAmA/wiki/index#wiki_14._voting_etiquette

i.e. AMAs are not for regular chatting (e.g. "I love you and your sandwiches!"), but actual questions to facilitate discussion/interaction, so the thread doesn't get clogged up by people telling Keanu how he's awesome rather than asking him things he can answer.

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