I post on reddit explained it a little better:
If you're a keyboard player this is much easier I think!
Macro an emote (that has motion when you're sitting down) such as /joy motion
Now sit at any bench/box/chair/etc and the timing of this next part is key. You have to almost simultaneously hit the macro and press w or s once. If you're successful, you'll do the emote while standing.
The easiest way I've found to trigger this is to actually click the macro on the hotbar with my mouse and then hit s on the keyboard to stand. I hope this helps!
http://www.youtube.com/watch?v=3whQuc_cT1I