Yeah, for the first playthrough, make sure you have five of the six companions in your team when you leave the Citadel and pick up the sixth as soon as you do so you don't miss out on the exposition. Subsequent playthroughs you can fiddle with this in any way you can, because The Dev Team Thinks of Everything
and there's hilarity (and a Tear Jerker
in the second game) to be had in it. Virmire should go last, also, BEFORE you go there, resolve all of Admiral Kahoku's plot thread. It's long, it sets up bits of the second game and it will be incompletable otherwise.
And no, you don't need to do the loyalty missions in order to "resolve the impossible situation" as the achievement calls it, you only need to have a high enough Intimidation or Charm skill.
Also, save before using any elevator on Noveria, they are glitchy as heck.
edited 13th Feb '11 10:37:32 PM by Noelemahc