Less Tits n' Ass, More Kickin' Ass

1- Observe real arms and how they relate to real bodies. Make a note where landmarks sit: shoulders, elbows, wrists, tips of fingers.
2- Move your own arms around and look at them. Feel how they move. Use mirrors to do this.
3- Generic shorthand is that the elbows line up with the waist and finger tips arrive one hand above the knee. Also, use motion arcs to figure out these distances when drawing raised and/or bent arms.
4- Did I mention observation? Because it’s important. You need to do a lot of it. Trust me.
Good luck and keep drawing!