FREDERICK the Great used to make his own coffee, with much to-do and fuss. For water he used champagne. Then, to make the flavor stronger, he stirred in powdered mustard . . . Now to me, it seems improbable that Frederick truly liked this brew. I suspect him of bravado, or perhaps he was taste-blind." (Serve It Forth, by M.F.K. Fisher)

It is equally difficult to believe that most people enjoy the taste of the more than 500 million cups of coffee consumed each day in our country. For the most part, very little thought or care is given to the preparation of coffee, and too often it is not much more than brown water instead of the magnificent brew which might have been.

Of all the elements that can greatly improve coffee-making, one of the most important is a good coffee-grinder.

Most people believe the coffee bean goes into an immediate decline once ground - and this is true, up to a point. Extensive experimentation by a group of leading coffee-tasters found that beans ground 12 to 24 hours before use and stored in an airtight glass jar under refrigeration produced a smoother and mellower brew than coffee used immediately after grinding. To ensure freshness, only the necessary amount of beans should be ground, and the remainder stored in a freezer to guard the flavor.

For grinding, it is not necessary to select a coffee mill with a large capacity - a six-cup pot of American-style coffee requires less than a cup of ground beans. What the mill must have, however, is an easily adjustable grind system and a pass-through grinding mechanism.

The adjustable grind system will produce the fine powdery coffee necessary for Turkish, Greek and expresso coffee, or a medium-to-coarse grind used in today's electric coffee-makers.

The cast-iron, clamp-on model by Spong is a replica of an old English mill. The grind is adjustable, within narrow tolerances by setting a lever in the back. It can be clamped onto a table or mounted on a wall. The removable container for the ground coffee does not have the capacity that it should and it is bother-some to empty it after two ounces. But it is hand operated, and therefore in conformity with the president's energy-conservation program.

The time honored classic wooden coofee mill is still being made in France, just as it was at the turn of the century. The solid cube-shaped base is filled with a drawer which collects up to four ounces of ground coffee. The crank handle extends from the metal top which slides back for filling the [WORD ILLEGIBLE] . A clip is set at any of five notches under the handle to adjust the grind. The advantages of the wooden mill are its price, quaint design and manual operation. Its disadvantages are that the drawer for collecting the grounds often retains bits of coffee which may become rancid if not properly cleaned. The grind selection mechanism also does not allow for the full range and subtlety of size that one would like.

The best of the electric coffee mills are the Clemex, Krups and Braun units. Each is neat, compact and made of easy-to-clean plastic. The grinds be set for any of a series of textures from coarse to power. The whole beans go into the hopper at the top, down through the grinding mechanism, and finally into the ground-coffee container.

The Chemex mill has a measuring scale on the hopper indicating how many beans are being used, as well as a scale in the storage container for measuring results. It also comes with a little clip attached to the storage container, so it can be placed in the refrigerator until one is ready to use the burns. The Krups model has a series of bracket mounts for attaching the mill to a wall or the side of a table, allowing additional counter space.

There are a number of coffee mills with a large-capacity hopper on top for the storage of unground beans. Reset this tempertaure immediately after roasting, coffee beans begin to go stale unless vacuum-packed; and the process of deterioration is complete in 7 to 10 days. The freshly ground bean should be stored in the freeze - not in the hopper of the mill.

In an attempt to provide a small appliance for every milling purpose, a number of manufacturers have produced mills utilizing propeller-type blades which determine the grind by the length of time the blades are whirling. These devices produce an uneven grind which results in an uneven brew.