TIP #1: How much a polarizer filter will darken a sky depends on the type of sky and your shooting angle in relation to the sun.
TIP #2: On a sunny day, position your shoulder towards the sun and your subject at a right angle to it. With the sun positioned high in the sky, maximum polarization will result in the horizon areas. When the sun is positioned low in the sky, maximum polarization will result in all areas situated in front of and behind you.
TIP #3: A polarizer has very minimal effect when used under a gray, overcast sky.
TIP #4: Remove protective lens filter when utilizing a polarizer.
TIP #5: Only utilize a polarizing filter indoors for reducing reflections & glare. Color saturation will be extremely minimal. Remember, a polarizer filter will reduce your lens-shooting aperture by up to 2 f:stops.
TIP #6: Combine an Ultra Polarizer and an 812 filter to obtain "Warm Polarizing" effects.
TIP #7: Combine a polarizer with a Tiffen Enhancing filter for dramatic color saturation. (Enhancing filter provides dramatic & deep saturation to warm toned. colors - much greater than color saturation achieved from a polarizer or a Warm 812)
TIP #8: Utilize a polarizer filter to control depth of field focus. This is the same principal, as a Neutral Density filter only a Neutral Density filter will render "neutral" colors as compared to saturated colors obtained from a polarizer. Neutral Density filters are available in greater light reducing densities as compared to a polarizer.
TIP #9: To determine a Circular Polarizer from a Linear Polarizer - turn polarizer around, view through other side into a mirror. If where filter image in mirror overlaps shows black - you are viewing through a circular polarizer. If the overlap portion views clear, you are viewing through a linear polarizer.