Last but not least, when you get to the "Last Stand" part, make sure of 2 things.
A: leave behind both garrus and Grunt and Saheed, while they are awesome, they are also the best survivors in the game, and they boost the survival of the other squadmates.
B: Take Miranda with you if you plan on blowing up the collector base (her giving the middle finger to the Illusive man is just plain awesome)
C: Whoever you take with you HAS TO BE LOYAL, after the last boss dies, anyone with you that is not loyal dies, when shepard jumps to the ship if none of your friends are there to catch you, you die.
I hope that helped. :)
D: When you are going to the area infested with giant robot insect swarms, you need a strong biotic, only 2 people are good here: Samara (Legendary Asari Justicar, and the biggest pair of...... heels in the galaxy) or Jack / Subject Zero (shaved girl, serious sociopatic issues)
Finnaly, there will be a second spot where you again have to choose a leader, again the only good choises are miranda, jacob, and garrus, anyone esle would die.
B: when choosing who leads the secondary squad, you have to choose someone who is used to giving orders and knows about tactics. Only 3 are good for that, Miranda (Who is a cerberus officer and a bossy snub to boot) Jacob (Who before working with cerberus was an Alliance Corsair Captain) and Garrus (Who before being recruited was leading a 10man team on Omega to cap gansters) Choosing a poor leader will cause that leader to die by a gunshot to the chest.
C: when you are choosing who will escort Chakwas and the rest of the crew back to the ship, send Mordin. He's REALLY fragile and even if loyal has a really high chance of getting killed on the last stand.
Fourth, you have to select the correct operatives for the diferent tasks on the final mission.
A: for traveling in the ducts and hackign the door, you have to select someone good with computers, only 3 people are good on that, Tali (her race is a race of mechanics) Legion (he IS a computer with 1100 programs on it) and Katsumi (Master thief and supreme hacker) If you choose anyone else, they will hack the door open but wont be able to shut it fast enough and will have a rocket to the face.
Secondly you have to upgrade the ship, buy the Upgraded shields, weapons and armor. If you dont, then when you start the final mission, before you even land on the collector base, 3 of your squadmembers die. (Who dies is semi-random, but it's usually either legion, thane, tali, jack, or kasumi, selected randomly) To Upgrade the ship completely, you have to harvest A LOT of minerals, it's a complete pain, while there are no cheat codes there are some "Trainers" that allow you to have 500.000 of every mineral to speed things up.
Third, you have to secure the loyalty of EVERY-SINGLE-SQUADMATE. There is a point in the final mission in wich you take 2 with you and the rest does a final stand, in this final stand, whoever is not loyal will get iced.
I dunno if it's too late for this tip but here's what you gotta do to complete Mass Effect 2 without anyone dieing.
First of all, when your crew gets kidnapped, you have to start the final mission IMIDIETLY. If you do any side-quest or main-quest AFTER they have been kidnapped, about half the crew dies. If you do 2 side-quests or main-quests AFTER they have been kidnapped, then almost all the crew dies exept for Doctor Chakwas and Kelly.
do more than 2 quests and everyone but Chakwas dies.