How to care for a flag really depends on two factors: the flag material being correct for the weather conditions in which you fly your flag; and that your flag is properly stored if you won't be flying it for any length of time.
In terms of choosing the best flag material for your flag, be aware of the kinds of environmental stresses your flag is going to be in contact with. Some materials do better in wet weather, harsh sunlight, sea spray, urban environments (where there are lots of air-borne pollutants), or high winds.
So choose your flag fabric carefully! Make sure the fabric is a quality fabric that really is designed to "weather" the kinds of conditions in which your flag is going to be flown.
What stresses out a flag
Because flags are constantly moving and under constant stress, it is important to make sure your flag can fly freely without hitting or constantly banging up against any obstructions. Flag placement as well as the kind of flagpole you use can help with this: Some flagpoles fully rotate while others attach to buildings at certain angles. Some poles come with adjustable heights while other poles are fixed.
While a flag is flying, it is under a variety of environmental stress. Not just sun, wind, or rain, but air-borne pollutants and contaminants also can wear a flag down. You can preserve the life of your flag simply by occasionally washing it, by hand, in a gentle detergent, and in cool water. It is that simple.
Storing and keeping your flag clean
If you are going to store your flag for any length of time, consider giving it a gentle wash beforehand to remove any dirt or pollutants that can eat away at your fabric. Consider it like washing the underside of your car after a long winter of driving on roads sprayed with salt and other chemicals to melt ice and snow.
Finally, if you are planning to store your flag for any length of time, make sure it is completely dry and properly folded. Tradition and respect dictate that you do not store your flag on the floor. Other than that, you can simply keep your cleaned and folded flag in a box or any other storage area. If you prefer, there also are flag display cases specifically designed for displaying a folded flag indoors.
Not only is taking care of a flag pretty easy, but a little care will go a long way to ensure the durability and bright colors of your flag.
Let if fly!