The lights are on
Here's what has proven for me to be a surefire way to get all of your squadmates back from the so-called "suicide mission" alive and well - this is the strategy that's gotten me through 3 out of 3 playthroughs with no casualties, including one run on Insanity mode.
First, remember that loyalty is key. Obviously, this means you need to complete any and all loyalty missions. However, it also may or may not be important to continue personal conversations with your squadmates after their mission loyalty is assured. Any time you have a chance to ask a squadmate about themselves, take it. Not only may it help to ensure their survival, it's just plain fun - especially when you get to hear Mordin sing Gilbert and Sullivan.
This also means you'll need to decide a morality path (paragon or renegade) and stick to it. At two different points in the game, two of your squad members will get into a tiff following completion of both their loyalty missions - Miranda and Jack first, Tali and Legion second. You'll need to have a high enough score to choose a special conversation path, or else you will lose the loyalty of whoever you don't side with. Boosts provided from leveling up your specialization skill tree can be very helpful in this regard.
As for the mission itself:
First, make sure to get the three necessary ship upgrades so that all squad members survive the initial approach - this means Jacob's armor plating, Tali's shield upgrade, and Garrus's Thanix Cannon are all vital. Other unique upgrades for squad members may or may not ensure their survival, but at the very least, they'll make the mission itself easier. Get them all.
Then, the specialists. First, you'll need to pick a tech specialist and a fireteam leader. The key word for the tech choice is SPECIALIST. It sure is sweet of Jacob to volunteer, but don't let him do it. Tali or Legion are the only choices - personally, I went with Legion every time. For the fireteam, you'll need someone experienced in command. Remember how Garrus (mostly) successfully lead a team of a dozen against the entirety of organized crime on Omega? Yeah, pick him. Remember to hit the cooling vents before the pipes overheat and your techie dies. And if you're in a pinch on the last one, you can ignore the enemies and just storm straight to it. Hitting the switch will end the first segment.
Next, you'll have to choose a fireteam leader, a biotic specialist, and (if you choose) an escort for your crew. The crew doesn't have to survive in order to get the achievement (and if you don't give them an escort, they won't), but send Mordin with them. For some reason, people have had trouble with Mordin dying during the mission even if all the right choices have been made - this will prevent that, as he should reach safety with the Normandy crew.
For the fireteam leader, stick with what works - Garrus. For your biotic specialist, again, SPECIALIST is the key word. Again, your squad tries to lead you astray. Miranda says that "any biotic could do it". This is simply not true. You have two choices. Samara/Morinth and Jack (I've done it with all three and it's worked every time). This should again get you and your entire squad to safety.
As for the final battle, there seems to be some debate. Some say it's better to choose from squad members less suited towards a straight defensive fight, like Jack, Legion, or Tali, as they won't be able to "hold the line" behind you as well. Others say it doesn't matter at this point. But the only problem that seems to arise from this issue is Mordin's otherwise inexplicable death, and if you've sent him back already, it should be a big deal. I went into the last battle with Miranda (for her heavy warp) and Grunt (for his squad incendiary ammo) and came out just fine. If you do find yourself encountering odd squad deaths, try changing up your team.
Well, that should be it. Remember: loyalty, ship upgrades, and correct squad choices should get you and your team out unscathed. They say it's a suicide mission. Prove them wrong.