A couple of my tips:
* Can't find one of the historians for the Vulcan diplomatic mission? Go down the stairs. Keep going the same direction, around and past the fountain. You'll see a faint trail going up a steep hill, which ends up being marked by huge torches. At the top of the hill is a round building. If you think of the building like a compass, and you're at South on the building, the last historian is at Northwest, just outside the building behind a little hill. Very hard to find but one of the keys to solving the mission.
* Have an unsupported video card, but want more detailed screen captures of your characters and ships? Go into Options > Video and crank the video quality all the way up. Your sound and manoeuverability will be shot but you'll get more details in for your pics. This is best done at a tailor or ship customisation station, or at an idle point in a mission.