Apparently Metro 2033 has 2 endings with one requiring you to complete various good-guy actions throughout the game. I've read that you need to use a lot of stealth to avoid killing people to reach the good-guy ending. The specific level 'Frontline' was really rough for me so I am wondering what tactics I could use to get through it stealthily.
Patience. And a lot of saving. And a lot of patience. It took me a few hours before I finally got through it. The guards generally follow the same set path every time you reload it. When you get closer to the end, you should be able to just sprint past the last few guards. The extremely difficult part is getting past the fascists (i think its the fascists....the ones that are facing you as you sneak through the level).
Extinguishing the lamps and taking out lights with throwing knives also helps. You can tell which way the guards are facing by the lamps on their heads.