I have not been able to figure out stance changes in macros yet.  I've also been trying to figure out how to make a pause inside  macro, but no luck

Currently the devs do not allow a pause ingame. I read on a board somewhere that a dev posted that they were not planning on including it.  Anti-Botting

This does not work for me, I just keep getting the message "You don't have knowledge of that".

In reply to when/how you get stances, you get stances at level 15 when you choose your martial style. For example, Harmonious Style gets Tiger, Harmonious Body, and Crane.

Small derail....

I wish they would put in some kind of /pause. It prevents us from using feign death in any of our macros. If you try to make a macro starting with feign death, you cannot do any new actions until you actually finish feigning your death. So for a specific example I cannot make a macro to

/feign death
/stand
/Nerve Strike

Granted thats not correct but you get the point. This macro will fail at /stand saying I'm not ready to do that yet. Thus making us have to use nerve strike a three step process of fd, stand, nerve strike. Still something easy to do, but that process really belongs in a macro.