In which direction does the Milky Way rotate? We don't have a photo of our Milky Way the whole, all the pictures are artists' interpretations showing a bulge, a central bar, and several spiral arms. The milky way is spinning. I would like to know: 

a) Does it spin with the arms trailing or leading?

b) I read if the direction of spin clockwise or counterclockwise depends on whether the Milky Way is observed from above or below. I don't understand how the direction of spin (clockwise &amp; counterclockwise) depends on the point of view of the observer.
The Milky Way has arms that form due to density waves. Like the majority of spiral galaxies, the arms are trailing. Individual stars orbit in circles (roughly), neither towards or away from the centre.

If you consider a common map of the Milky way (imagined from a point North of the Earth, Celestial North is not the same as Ecliptic North, which are both about 60 degrees off from Galactic North)

The stars in the galaxy would be moving in a clockwise fashion.

If you were to view from the other side, it would be as if you had made a mirror image of the galaxy, so the motion would be counterclockwise. If you look at the back of a clock, then from the wrong side, the hand would move counterclockwise. However the rotation of the galaxy is still with its arms trailing.

There are some galaxies that rotate with arms leading: NGC 4622 is one example.