The Phoenicians are known to have smoked the tuna they caught along the Sardinian coast. They also explored the Cabras Lagoon, on the western side of the island near what is now Oristano. It's quite large, extending over 2000 hectares (about 7500 acres), and teeming with muggine, or gray mullet. Which they eagerly caught, and when they realized that the hens were replete with roe, began to salt it to preserve it. Production of bottarga has continued since then, and is still a major local industry.
Bottarga di muggine is made from the hen fishes' egg sacks. Pieces of bottarga di muggine range from 3-8 or so inches in length, or 7-20 cm, and if you purchase a piece, select one that has a white rim on one end that resembles a fingernail. In terms of flavor, bottarga di muggine is more delicate than bottarga di tonno (the other kind made in Sardegna), and has more of that essence of the sea to it.
Bottarga should be consumed shortly after purchase; though it is of necessity packaged in plastic to keep it from drying out in transit, it suffers being wrapped up. So upon getting it home, unwrap it and enjoy it. At the presentation I attended were given bottarga with finely sliced raw artichoke hearts, which provided a very interesting taste combination, with the bitterness of the artichokes making the bottarga seem sweet, and quite complex.
Another very tasty option would be to butter slices of toasted bread with unsalted butter, and sprinkle them with finely shaved bottarga.
The most common way to enjoy bottarga however is in pasta sauce: Cook your pasta, and while it is cooking shave the bottarga into a bowl and stir in some good quality extra virgin olive oil. Turn the drained pasta into the bowl and mix well. That's it; cooking bottarga makes it bitter, and that's something you don't want.
In terms of proportions, figure, for a healthy pound (500 g) pasta 60 g (2 ounces) bottarga and 1/3 cup olive oil; this will serve about 4. One could do much, much worse.