So, with the cold weather arriving it is likely that more eagles will be arriving. Last week, there were more photographers than birds so hopefully that will change. First, one should call the hotline (888) 457-4076 to determine how many generators will be running (this determines the flow and likely areas where the eagles will be fishing - closer to the dam vs. downstream). Where one chooses to shoot is entirely dependent on the individual photographer. I generally aim for the "fishing pier" which is closer to the dam itself when the flows are "normal" (2 generators). That can change quickly, and I've been there when there have been unanticipated releases which will raise the water levels rapidly 3-6 feet, so be prepared. Many photographers prefer the "fence line" though I don't like the elevated position and shooting across the towers/island. When the water is really high, there will be some action near the boat launch though this is fairly rare in my experience.
As to when to arrive, weekdays are generally less crowded than weekends though as the colder weather sets in more photographers arrive. Last week there were at least 100-150 photographers on weekdays. Weekends are crazy and unless you arrive very early, you'll end up parking offsite and having to take the shuttle (bad). While many people arrive before sunrise to stake out a spot, recognize that fog/atmospherics are prevalent, and you might not be able to shoot in the earliest light. At this time of the year, the sun is typically rising almost directly down river so the early morning yields strong side lighting. Nonetheless, with the sun's trajectory, it gradually moves behind you and by early afternoon 2-4 pm you'll be on perfect sun angle. Depending on whether it is sunny or overcast, one can shoot most of the day if/when the fog/atmospherics clear. My recommendation is to plan for weekdays if possible and figure on spending a couple of days to maximize the experience. Conowingo has become a real destination, and the vibe has changed significantly from a couple of years ago. The "regulars" are still around though it is becoming more like a "festival" atmosphere. If you can filter out the nonsense and focus on the experience of hanging out and meeting some cool people and making some great images, being there is really enjoyable.