From Before I Play
- You get "morality points" towards the good ending by exploring (and looting) out of the way spots, listening to incidental conversations all the way through (civilians and enemies both), doing good deeds and avoiding enemy casualties. If you explore well enough, you can skip the pacifist angle and still get the good ending though.
- Don't worry about getting separated from your allies. They will always wait for you to finish exploring, safe and sound.
- Many stealth sections are based around advancing as far as you can without being detected to trigger a conversation that will make the enemies move on to more convenient spots.
- Take your time, explore, soak up the atmosphere. It rewards exploration and you're missing out if you don't poke around - especially in the stations.
- The revolver is a very reliable weapon and can take you through the entire game, though not worth silencing. If you're killing people stealthily the throwing knives are a much better option anyway.
- Listen to NPC chatter. Seriously: the stories they tell are absolutely beautiful at times, and really draw you in.
- Early on you get a chance to spend some time with a prostitute. Don't do this unless you want to lose all your money.
- Buy SHITLOADS of ammo at every shop (but when a dude tells you to buy gas mask filters, get those first)
- The game will automatically force Artyom to switch filters when one runs out. The only reason to switch manually is to avoid the distraction in the middle of combat / if you hate listening to choking noises.
- The Helsing gun is very powerful and has reusable ammo - you pretty much need it to finish the game as one part has a lot of strong enemies that simply suck up ammo.
- Throwing knives, if you score a good hit with them, will stealthily instakill most enemies and you can pick the knife back up. Don't forget about them.
- Long-range scopes are practically useless - you never fight at a range that will require sniping.