I've found impossible mode kind of hard, but I've found a few ways to help noobs and vets alike pass impossible levels.
1. Some weapons are found on impossible mode only (ex: Sniper Rifle YippeKiYay). They are very useful once they're obtained.
2. Time warp will help you dodge, mirror, and aim easier (make sure you take breaks in no-man's land to regenerate energy).
3. Ray guns are rarely seen, which means almost every bullet can be mirrored.
4. I reccomend lite suit for Easy and Medium difficulties, but use Heavy for Hard and Impossible (Speed isn't really needed unless you're rushing through, in which case switch back to lite).
5. Use Rocket Launcher to take out Android SLC's and Assault Rifles for Android T's.
6. If you don't see any enemies, I would recommend using a human shield (with kinetic module) in front of you, because they might be waiting to ambush you. Especially on a two-faction level (level 1 for example, you could cut one of the first two dead usurparations in half and put them in front of you, which would make civil securities see the body and shoot it, thus discovering them).
7. Beat the level on Easy first, then Normal, then Hard (tip for noobs only) to raise your skills.
8. Multiplayer can help train you.
That's all you need to know. Now go kill some enemies!!!!