Everyone's arms do different things, but some motions seem pretty standard just due to balance. Most ppl's arms go down when they suck their legs up...except Matt Town who is fucking awesome and leaves his arms pointing to the sky.
What tricks make you do weird arm shit? For me, regular kickflips make me whip my front arm back and up while my back arm stays down, which doesn't happen for anything else. It's super fuckin weird but I guess it's just how I do em.
(shoutout to Northern Company)