Almond flour is made from finely ground blanched almonds. The only thing that distinguishes almond flour from almond meal is that the meal is more coarse. They can typically be used interchangeably in quick breads, muffins or pancakes.
Almond flour may be made of blanched almonds or almonds with skins on; check the product label if you require one product over the other.
Nut flour has a high oil content and will go rancid rather quickly. It is best to make in a batch for your specific recipe. David Lebovitz suggests using some of the flour or sugar called for in the recipe when blending the flour. This helps to prevent the flour from being heated and becoming oily.
Place nuts and about 2 tablespoons of the flour or sugar in a blender jar with a sharp blade. This is probably not the best job for your twenty year old blender if you've never changed out the blade. Alternately you can use a food processor.
Just pulse the blender or food processor on and off until the nuts are ground to an even consistency. Don't expect a perfectly refined texture because nuts don't grind very evenly.
If you have excess flour it should be stored in the refrigerator. Place the flour in a jar with a tight fitting lid.