If I perceive http://en.wikipedia.org/wiki/Cross_product correctly, then to determine the cross product With a right hand, let:
the 1st vector in the cross product = your index finger = in red below
the 2nd vector in the cross product = your middle finger = in purple below
Then $\mathbf{\text{ first vector } \times \text{second vector } } =$ your thumb = in green below.
My picture confirms this.
Yet what about with your left hand? Regarding the picture below, the blue vector is supposed to denote the final cross product. I work backwards to find that the left hand must satisfy:
the 1st vector in the cross product $= \partial_z \, \mathbf{r} =(0, 0, 1) $ = in black = the thumb
the 2nd vector in the cross product$= \partial_\phi \, \mathbf{r} =$ in green = the index finger ?
Then $\mathbf{n} = \partial_z \, \mathbf{r} \times \partial_\phi \, \mathbf{r} =$ in blue = the middle finger.