I am halfway through my Insanity playthrough of Mass Effect 2, and I feel compelled to share what I've learned with people who might be considering the same thing.
The watchword when playing Mass Effect 2 on Insanity is "survivability". When you upgrade a teammate's skills and have to choose between giving them more weapon damage or more health, take the health. When your squad goes down, your chances of survival drop drastically. I recommend taking Grunt and Jacob in your squad, earning their loyalty, and then dumping as many skill points as you can into Barrier and Fortification. (When you max Barrier/Fortification, take the "Heavy" evolution. In combat, a barrier won't have the opportunity to last for three minutes; you need to be able to soak up as much damage as possible.)
Biotics are your best friend. If you try to use firearms all of the time, you will run out of ammo in a heartbeat. Biotics continuously recharge, making them your first choice in combat. But if enemies try to charge you, you will need something with a bit more kick. THAT is when you need a gun. For this reason, don't build up a character who is useless with firearms, just for the biotics.
Early on, when you don't have the loyalty of your squad members yet (and therefore do not have their best abilities unlocked), they will be pretty useless in a firefight. Instead of bringing them to the front, order them to set up a fallback position. You can take care of yourself for a bit, right? Then, when you get overrun, fall back to your teammates and use their help to kill whatever is chasing you. Then move back up to take the enemy on by yourself again.
Don't put yourself directly into cover. Find a tall piece of cover that shields your whole body, and edge around it to shoot at enemies. This leaves you much less exposed than leaning out of cover to line up shots. If you are using shockwave as your main biotic power, you can blast enemies right through cover, leaving you even less exposed.
Enemies can't open doors, so if you get the chance to hit them with shockwave from the other side of one, do it. So what if it's dishonourable? Open either the weapon wheel or the power wheel to view your radar and line up your blasts.
And save up your heavy weapon ammo and medi-gel for the Collectors. You will need both.
That's it. That's all I can teach you. Just remember: Biotics, don't stick to cover, and survivablility. If you have any further questions or just want to compare notes on Mass Effect 2, post a comment or send me a message.
ADDENDUM (20th, Feb): I recently ran into some trouble with the first fight on the Collecter Ship. Apparently it's one of the hardest fights in the game (Harbingers, Scions and virtually no cover). This video helped me: http://www.youtube.com/watch?v=pf0i3BpxlTc. By the way, this is why I say to save your medi-gel and heavy ammo for the Collectors. And unless you are playing a Soldier, don't count on your ammo holding out the way this guy's does. In fact, Sentinels have the best armour - if you were to take my "survivability" mantra to heart, you might consider playing as one. I started my Insanity playthrough as a Vanguard (stupid, I know), but now that I've come this far, I'm not turning back. I refuse to do the sodding Colony Defense mission again. Not to mention Grunt's Rite of Passage. *shudder* That was a freakin' nightmare.
[tags: mass effect 2, insanity]