Eggshells crushed into coffee grounds make for better brew. By accident discovered hard-boiled eggshells make even better brew. Research reveals eggshells were used to prevent grounds from floating flecked into the mouth; it seems to work. Another method of achieving this is to let your joe cool for a short while then add a small amount of cold water. This puts into function some law of physics and drags these pesky grounds aground. It is also suggested the eggshells make your drink taste better because the calcium and various other compounds within absorb the the more bitter acids while leaving behind the fun bits. Word of caution: some people are allergic to eggs and just might go into anaphylatic shock. Swell up something terrible and turn blue. Would be wise to inform guest of special ingredient before breaking out the percolator.
I use New Orleans French Market Coffee and Chicory: it makes for a frothy brew, its foam guinness-like. I blend it with dollar store grade but just as tasty as premium brands Hill Bros Dark Roast, 1-to-3 ratio, for a nice morning buzz.