Water filter - when do I change?
The water filter inside the refrigerator section should be replaced about every 4 to 6 months, even though they will successfully filter your water for up to a year.
All water contains particulate material and bacteria which the filter will strain and then hold within its core. But every filter will eventually reach its limit. After about 4 months the bacteria level within the filter can exceed it maximum, and therefore may start to redeposit the bacteria back into the water as it passes through filter.
Water filter - how do I change?
Most water filters simply screw or snap into a receptacle inside the refrigerator section. Some are accessed near the bottom front edge of refrigerator. Most are mounted on the rear wall inside the refrigerator section. If filter cannot be located, look for a tag or sticker inside the refrigerator indicating its placement. If cannot find filter look for plastic water lines in the corners, or behind the crisper drawers, then follow the water lines.
Some filters require a special tool to remove. Others require that an O-ring or seal be changed in conjunction with the filter. Before replacing read all instructions associated with the new filter.
For step by step directions see your Care and Use guide. Each manufacturer uses a different type of filter, and filter-mounting method. They are not interchangeable.
If you already have a new filter the installation instructions may be printed on the box.
Most manufacturers will answer this question on their website. 

Water filter - can I add external filter to the water line?
Yes, a filter in the water supply line feeding the refrigerator will provide filtering.
If added to the water line the weight of filter (and the water inside it) must be supported by securing filter assembly to wall behind refrigerator.
Before installing verify that will provide same quality of filtering as type provided by the refrigerator manufacturer.

Water dispenser - water not cold!?
These devices are water dispensers, not water coolers. They are always associated with an ice dispenser so that ice can be added to the glass first, thus making the water cold once it enters the glass.
Some refrigerators contain a water reservoir. They can give the impression of colder water entering during first few glasses of dispensed water since they only hold a small amount of water. Their purpose is not to store cold water but rather to compensate for  warm water that initially enters the glass from the water line at the back of the refrigerator. 
To cool the water an amount of ice should be added to glass before water is dispensed.

Water dispenser - water tastes unusual!?
An unusual taste from a water dispenser may indicate it is time to change filter.
If used infrequently water may be picking up odours leeching from the plastic water lines. Usually resolved by clearing lines of stale water by disposing of first few glasses dispensed before dispensing water to be drank.