Predicting polarity using geometric shape

I'm having trouble with certain polar molecules that "seem" to be nonpolar. For example, the hydrazine I drew looks like this:


I'm not supposed to draw in the electrons, but they're there to show you. Both the left and the right NH2 seem to cancel out each other's polarity. How am I supposed to explain the polarity of the hydrazine molecule using just the geometric shape?