often you see rigging tutorials with a character that has its arms straightened out by 90 degrees to the body. this looks advantageous as it makes positioning joints very easy in a front view. but it is more practical to use a default pose with more relaxed arms (same for legs, so don’t use the ‘da vinci pose‘ as a default pose to rig), so they’ll have an angle like 45 degrees. this makes positioning the joints more difficult, but here’s where construction planes within maya come in handy.
so let’s assume you have your arm geometry visible in a front view, go to create > construction plane and enter the options window. set the size to 12 (or whatever size of units you need to surround the arm) and pole axis to xz. now rotate the plane to have the same angle as the arm and just make it live. this makes a grid on the plane visible so you can easily position your joints on this plane in a top view. you also may want to turn off the base grid in order to have only the construction plane grid visible: display > grid.