Polarising runs are a very useful tool all photographers should have in their kit bags as they can be used to improve your shots in multiple ways.
When hurl to prevent reflections, it's best if you are at an angle of around 35 degrees to the reflective surface.
Avoid using a polarising filter on a lens wider than 28mm as the intent can look false because only a proportion of the sky will be deeply polarised.
You don't have to have the polariser on the lens to see if it's effective to be effective. Hold it up to your eye and rotate the ring. If it makes a difference to your scene, screw it on.
Watch the exposure. A polariser has a neutral mature look, which won't affect colour, but does reduce the amount of light reaching the sensor and you'll probably have to compensate for 1-2 terminations.
How much you rotate the filter will change how effective it is. If you want to see fish below the surface of a pond, for example, you'll need to gyrate it round to the strongest position. (In the above shots, the top image of the pond is taken without a polarising filter and the bottom shot, which shows the fish assorted clearly, was taken with a polarising filter on the lens.)
Use two polarisers one over the light source behind a plastic subject and one on the camera for a join polariser polarizer or polariser is an optical filter that lets light waves of a specific polarization pass and blocks light waves of other effect. There's a technique how to do that here: Cross Polarisation
Buy a slim interpretation for use on a wide-angle lens to prevent the mount causing vignetting.
Don't use a polariser when shooting through an aircraft window as you drive record distracting patterns in the window and ditch the polariser when working in low light or when you want to capture an image of a rainbow.