Arm movement is one of the most diverse variables in running form. There are not too many runners whose arm movements look alike. Unless we are talking about those people with perfect form (check out Ryan Hall in youtube if you need arm-inspiration).
Arms should be parallel to the body, bent at the elbow, hands pointing straight ahead, and your hip bone should get visits from your elbow and wrist.
No chicken wings, no hanging arms, no boxing arms, no arms crossing the belly button. Make sure they are relaxed too.
And keep in mind, just so you know how important this is, that whatever your arms are doing, your legs will do.
Pump your arms when going up a hill, your legs will shorten stride length. Relax your wrists, and your ankles will follow.
So, when you know your form is form is flailing, focus on the arms first.
More on Running Biomechanics
runningandthecity 
Very useful tip!
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