Stay Calm

 4. Keep every door open that you can.

5: Stay vigilant when looking for keys and pages I have found myself doing this mistake plenty of times and missing a page.

6: Watch out for steam pipes they can burst and down you, you can also turn them off with a valve.

7: You can revive yourself with a medkit by holding left click and revive teammates with right click, medkits become more rare the higher the difficulty.

8: When you run she will go to your location (still not sure yet, so take this with a grain of salt)