When I originally played the game after it came out (and before DLC), my first and only run everyone came out alive.
 
Now today I just finished the game and TWO people died. I can't figure it out.

Vents: Legion
Squad Leader 1: Zaeed
Barrier: Jack
Squad Leader 2: Zaeed    
Escort Leader: Jacob
Final Team: Tali and Garrus

Died: Legion (First set of doors), Zaeed (Second set of doors)

I was loyal with everyone except Zaeed. I just can't figure out how Legion died.

Beat the game (2nd Playthough) and everyone made it, I was loyal with everyone minus Jack. I just never assigned her to a role (obviously) I picked Legion for the Vent, Garrus to lead Team 1. Then I picked Miranda to lead Team 2, Samara to make the bubble and Mordin to lead the survivors back. Then I think I picked Garrus & Legion as my final squad (no particular reason, I just like them both)  
 
Funny thing though, Miranda was shot in the gut as the 2nd doors shut. But she just recovered from it and was completely fine.  
 
But on my original play through quite a few people died, I never prepared the ship at all. So 3 people died straight off the bat. Since I screwed up Samaras loyalty mission too one of my members were taken by the flies. All the good characters died so I ended up just starting over. I'm not playing ME3 without Garrus. :P

i was on casual and the only person i had not lolyaly was jack and jack died randomliey i took maranda and grunt with me and mordan took the escort so i think that sucks i was going for a perfect save and i dont have a save to do the mission over so i have to restart and i followed every thing the guide said oh well i didnt like jack that much anyway

Just beat the game for my first time wow, what a game! so happy part 3 comes out this year. i can barely contain myself. 
 all my members survived and they were all loyal and i was playing on normal.
 
for me it was 
Legion, Garrus, Jack, Garrus, Mordin, Miranda + Samara

Fuck yeah, got it first try. Thanks, duder.

Just beat the PS3 version with zero deaths. I had full loyalty for everyone except Jack, which I lost in the argument with Miranda and was unable to regain.
 
My selections: 
 Vents: Tali 
1st and 2nd Squad Leader: Garrus 
Shield: Samara  
Escort: Mordin
Final Team: Miranda + Grunt

I beat the PS3 version on Veteran difficulty with no squad deaths but I took my time finishing the DLC and other assignments so I lost all of the crew.  I didn't use a FAQ for this; I'm pretty stoked about that
 
Vents:  Tali (I don't trust the machine) 
1st Squad Leader:  Garrus 
2nd Squad Leader:  Miranda  
Shield:  Samara 
Escort:  Jacob 
Final Team:  Morin & Grunt 
 
Everyone was loyal except for Zaeed.

Got all loyal except for Zaeed.  I just couldn't have those innocents die in the factory and I didn't give a shit about his character so I found his loyalty pointless.  Then I picked Miranda over Jack.  On normal I was able to keep everyone alive picking all of the right people for their jobs.

 Vents: Legion
1st and 2nd Squad Leader: Miranda 
Shield: Samara  
Escort: Tali
Final Team: Miranda + Garrus 
 All loyal all lived. 

I think there is a lot of speculation in the guide. I completed the suicide mission on the Insanity difficulty with no deaths and my crew being saved. My DLC included the Firewalker Pack, Zaeed, and the Cerberus armor and weapons. I had every upgrade I could possibly get except for one heavy skin weave. When it comes to upgrades, I know for a fact that the armor, shield, and weapon upgrade for your ship is required. However, perhaps Jack's implants and Mordin's tech damage upgrade are also required, but even then I am very unsure. The rest of the upgrades are just for personal progression and to make life a little easier when fighting through the Collector's base. I played the PC version for this and I was full paragon soldier, in case anyone was wondering about those details.

This is how I fought through the mission and I actually used all the squad mates available to me.

Part 1: Vents
Tech Expert: Tali
Fire Team Leader: Garrus
Squad: Mordin and Legion

Part 2: Seeker Swarms
Biotic: Jack
Diversion Team Leader: Jacob
Escort: Zaeed
Squad: Grunt and Thane

Part 3: Endgame
Squad: Miranda and Samara

I am kind of glad I did not have Kasumi for it would have made it uneven.

I kinda regret reading this before playing through that last mission. (Especially since now Jack is alive in my playthrough, hate that woman.) I won't expose myself to anything come Mass Effect 3 time. 

After Killjoi hint I`ve used, all loyal, all ship upgrades (aside from Med-Bay Upgrade):

Vents: Legion
Leader: Garrus (1st and 2nd)
Escort: Mordin
Barrier: Jack with implants
Final Team: Miranda+Grunt

And finished will all members alive!

One name... Garrus. Everybody survive. People need guides for this kind of stuff? Andraste's tits... Well I should not be suprised because I saw people having problems with the "puzzles" in the FADE quest in Dragon Age 2.

 This method has worked for me on every difficulty with all loyal.

Vents:                                         Legion
1st (Fire) Squad Leader:        Miranda
Shield:                                       Samara
2nd (Fire) Squad Leader:      Miranda
Escort:                                       Mordin
Final Team :                             Miranda and Grunt
Sexual Intercourse:                Miranda on normal - Jack  (non romance) casual sex on insanity

Vents: Tali

1st fire squad: Miranda

Shield: Samara

2nd fire squad: Miranda

Escort: Mordin

Final team: Grunt & Miranda

Everyone Loyal. Difficulty Casual. Thanks for the help @Killjoi

Is it possible that members who aren't loyal can survive?

I chose the wrong choice in Tali's loyalty mission and she isn't loyal Miranda isn't loyal because I chose Jack instead, I failed Thane and Samaras loyalty missions

That's all my favourite characters, and I don't want them to die

@DiggyHole333: I don't think so, sorry

@bio595: oh, well thanks anyway

This was extremely helpful, thank you for doing it :D

Used this one:

and I can confirm it's working perfectly on Hardcore difficulty. (Maxed out Vanguard, Paragon, all squad mates loyal)

the fuck is wrong with you?

Tali for the vents, Miranda for leader on both squads, Mordrin as escort, Jack for sheild's, final team Kasumi and Thane. Got through just fine everyone lived even the crew.

Hey people i'm having a lot of problems on this section of the game, my vent person keeps dieing on my and i'm getting really stressed out. I used Legion what is fine, but whom ever i pick as 1st squad leader he dies, garrus, miranda, jacob ext. I am struggling to keep sane now, he is loyal to me so why is he dieing? im having a lot of problem with my ME2 going from loading screens make game stop responding for like half a min and form my DLC's not showing up in game, i don't want this as well to fuck up the game. I hate it when somone dies i have to restart the misison, but on the 1st death i have to restart it from before i go in Omega 4 relay, that means watching all the bloody cut scenes again and not being able to skip it -.-

@sgtmathias: not for me, Legion dies every time with every squad mate, its anoying i duno how to get past the vents with somone not dieing. and yes they are all loyal.

Vents: Legion

1st Fire Squad: Miranda

Escort: Mordin

2nd Fire Squad: Miranda

Shield: Samara

Final Team: Tali and Miranda

Everyone loyal except Jack

Everyone survived

Difficulty: Casual

Romance: Jacob

Just wanted to say, this helped on my 2nd run through on ME2. Got ME2 as part of a free game dealio on Origin... an loved it, so much that I busted a move & snagged a triple play pack of ME1, ME2 & ME3... sweet deal @ that... : )

I also grubbed a hold of every DLC that I could get more so, mission wise... did snag a suit/weps DLC or 2 to boot...

On to my 2nd run through, ( which with 1st run through... I lost Zaeed, Garrus & Jack in that run through... sad *sigh*(dramatic pause)... any who... )

Game set to casual, since I wanted story line, plus wanted to get a feel for the combat 1st. I ran down every side mission I could grub on to, did loyalty missions in the following order: Miranda, Jacob, Kasumi, Mordin, Grunt, Zaeed, Garrus, Jack, Thane, Samara, Tali & finally, Legion... Side note, as for romance, tried to keep it low key so as to remain loyal to Liara, but... somehow ended up doing the bed bounce with Tali... not exactly sure how that happened *shrugs* will have to see how things go with ME3 after that occurrence. After completing the loyalty missions, I did slow poke about a bit, before jumping through the Omega 4 Relay... but was nothing mission related, revisited the Shadow Brokers lair, to grub up on ezo, platinum, palladium, iridium, an any additional upgrade items that I could get, so didn't lose any crew... sad for the colonists... ahh well, back to the Suicide squad line up...

Had ship upgraded on all but the med bay upgrade since you regen facially throughout the game play so no need for that upgrade on the ship... had everything else upgraded to the max, except for pistols... did have it 5/5 instead of the max @ 6/6, as far as I know of... so no big loss there...

So, for final battle:

Act 1:

Vents: Kasumi

1st Fire Squad: Miranda

Act 2:

Shield: Jack (nice seeing her do a shock wave with the shield bubble, right as we got to the doors, by the way... evil grin)

Escort: Mordin

2nd Fire Squad: Miranda

Took Samara & Tali with me, Samara for her biotics ability & Tali for her Combat drone ability... keep them suckers flying from Samara hitting them with throw (evil grin) and distracted with Tali's drones, buzzing them... leaving me free to dispatch them... with extreme prejudice, of course... *evil mad scientist laughter, think laughter @ end of Thriller by Michael Jackson*

and...

Final Team battle: Tali & Jack

End result: No lost crew, no lost squad members... Coolness extreme... :D

Will be making more run throughs, on different difficulty levels, an see how those go... Think I will also do a run through, as fem Shep, just for *hits & giggles...

DAMN YOU ALEX

There's a much more accurate chart out there. This explains every minute detail, including the math, efficiently.

@dooley: Don't show him this video...

(I like that at one point she walks from one Tali over to another Tali on the other side of the room because of how seamlessly they cut this.)