While I'm no expert on French press I can tell you what I think makes a great cup. The most important single factor in making great coffee is the beans. This doesn't mean there aren't 100 other ways it can go wrong-I've had some awful drinks made from great beans. My personal favorite single origin bean is Sumatran Aribica, and I prefer the rich array of flavors that a dark roast brings out of the bean.
The beans are at their prime until about two and a half weeks after roasting, so I always buy directly from roasters, and any beans I plan to keep longer than two weeks are sealed into an airtight container and frozen. Airtightness is crucial in preservation as coffee beans tend to absorb flavors from their environment, and I for one do not care to taste frozen potroast in my coffee. Airflow also oxidizes the fragile oils in the bean and so despite best preservation efforts, unsealed beans at any temperature will go bad!
Grinding should always be done moments before brewing as it creates a greater surface area thus speeding up oxidation. My experience is that french press requires a coarser grind than conventional brewing, as I once created a pot of muddy mess by finely grinding the beans.
I think thats about all I really have to say, just remember, some of this is science, and some is my own art and opinions. And if anyone happens to learn anything here---COOL BEANS!
Clair