I'm trying to get the Paramour achievement with Miranda. The problem is I didn't know that you have to choose specific dialogue options and I think I just chose all possible options, both good and bad, in the conversation that follows her loyalty mission. I am right before the IFF mission so I still don't have Legion. I have everyone's loyalty except for Jack's since I've heard that she confronts Miranda right after and I'll be forced to choose between the two and I don't think I have enough Paragon or Renegade to calm them both. I don't want to lose Jack's loyalty since I also want the No One Left Behind achievement, especially if Miranda isn't actually in a relationship with me. I can't tell though because the rest of the crew is super chatty but whenever I go to Miranda she just says that there's a lot of things to do and can't talk right now. I have talked to Mordin and he never mentioned anything about my involvement with Miranda and I heard he would if I was actually involved? So what is going on? How can I tell when I have enough Paragon to not lose anyone's loyalty? The bars underneath Shepard show that I'm missing about 2 of the upper bars or maybe 1 and a half more specifically. Should I try to do side missions and DLC to get more Paragon? 'Cuz I've heard it gets harder to clear the Paragon check the more missions you do :S It's all very complicated! HELP!

Progress further in the story and you'll eventually get that chance to get between her legs.

As for the "whens" and "hows" of the achievement, this wiki page might help you to know when you've effectively secured a relationship with a crew member. 
 
Ultimately, the Romance isn't going to be consummated until after you go through the Omega relay.  
 
As for the No One Left Behind achievement, it's hard to go into specifics about it without spoiling some of the events. Just know that Jack can survive the mission without being loyal to Shepard. There's a part where you need a Biotic-oriented party member to lead your squad, and you're given the option to choose which Biotic member (that is, Miranda, Jack, or Samara) will be that member. At this part, if Jack is not loyal, do not choose her.  

Romances in Mass Effect are all about talking to the same person over and over again, and being complimentary when its an option. 
 
Essentially, keep choosing the upper right choice in a conversation. That'll do something.

" Essentially, keep choosing the upper right choice in a conversation.  "

" @Sir_Ragnarok:  You sure you don't need everyone to be loyal to have everyone survive? I read somewhere that that was pretty much the prerequisite. "

" @Sir_Ragnarok:  You sure you don't need everyone to be loyal to have everyone survive? I read somewhere that that was pretty much the prerequisite. "

" @XII_Sniper: There was a really good thread at the beginning of the year that pretty much outlined what you needed to do to have a perfect ending. Surprisingly, there are close to a half-dozen ways to do it, or something. It's nuts.  "

Paragraphs. Also, just be yourself. LMAOVIDEOGAMES

" @Sir_Ragnarok said:

" @XII_Sniper: There was a really good thread at the beginning of the year that pretty much outlined what you needed to do to have a perfect ending. Surprisingly, there are close to a half-dozen ways to do it, or something. It's nuts.  "

Yeah that thread was a bit of a godsend for that game's last hour. Specially since it was spoiler-free.   See I had everything perfect in terms of loyalties, ship upgrades and picking the right leaders. Except for jack. I might have chosen her for escorting the survivors or something similar. Can't remember. One damn bad decision away from a perfect game. But I mean really... I didn't like Jack, so it was perfect enough for me. "

" @XII_Sniper said:

" @Sir_Ragnarok said:

" @XII_Sniper: There was a really good thread at the beginning of the year that pretty much outlined what you needed to do to have a perfect ending. Surprisingly, there are close to a half-dozen ways to do it, or something. It's nuts.  "

Yeah that thread was a bit of a godsend for that game's last hour. Specially since it was spoiler-free.   See I had everything perfect in terms of loyalties, ship upgrades and picking the right leaders. Except for jack. I might have chosen her for escorting the survivors or something similar. Can't remember. One damn bad decision away from a perfect game. But I mean really... I didn't like Jack, so it was perfect enough for me. "

Wait - does picking Miranda over Jack cause Jack to lose her loyalty? I thought as long as you do the loyalty mission for the character, they are loyal. "