Right hand rule: hold your right hand as if they are lines of latitude pointing in the direction of spin so for example on a globe of the Earth your palm would sit on the Pacific Ocean and stretch towards S. America and the Atlantic. Your thumb will now point to the North.
Another way to think about it. We define the North Pole as the pole where looking down the planet rotates west to east or counter-clockwise.
Another way to think about it is that looking at a planet at the equator from the orientation that it rotates left to right, north is to the top
Incidently, Venus has a retrograde rotation so it is upside-down with an axial tilt of around 177 degrees.