Still before the attack on the hospital, you will see several cutscenes. Follow the doctor's instructions and move your head. Then, you need to pick your new name, birth date (it is a good idea to pick a date close to the current date in the calendar, thanks to which you will unlock an easter egg), and pick your new face (face editor).
After you cut to the character, follow Ishmael. At first, you will crawl, but after some time you will start to crouch. Remember to follow all of the man's instructions and lie back down after he tells you to. After you get into a new corridor, start crouching again. Here, you need to get into the spotlights of the enemy helicopter. As quickly as possible, follow Ishmael and stick to the left wall (right under the windows), thanks to which you should not be spotted. After you walk away from the dangerous corridor, start running.
Follow Ishmael down to the lower levels, where you will have to backtrack, after a while, and reach the spot, where there are a dozen-or -so neutral people. After you walk into a new room, you will have to start avoiding the people armed with firearms, who start searching this place. Crawl over to the middle bed on the left. Wait for one of the enemies to search the neighboring area, behind the curtain. As soon as he leaves that area, crawl over there to avoid detection. You can now wait the search out.
Follow Ishmael out of this room. After you get into a new corridor, lie down and do not move. See the another cutscene and hold down the appropriate button to heal. Keep on your way. Soon Ishmael gives you a pistol (AM D114). First of all, fire it at the fire extinguisher in the blazing room. Walk up a little bit closer and after you get into the corner, stand behind the curtain. You can wait for Ishmael to handle the two opponents, or shoot them yourself (this will not prevent you from ranking S at the end of the mission). If you decide on the latter, try to target the heads of the enemies, thanks to which you will only need single shots to get things done.
After that, you can leave immediately, or pick an SMG (Sz.-336 SMG CS) from one of the corpses. Soon, you will walk into the main hall, where there are quite a few enemy soldiers. It is best to walk around them silently. To do this, go right and in the spot shown in the above screenshot, drop down to a lower level.
Very carefully, follow the right side of the hall - it is a good idea to crouch here, or crawl. On a regular basis, make sure which way the enemy soldiers are facing, thanks to which noone will spot you. As soon as possible, try to reach the hospital main exit . This will trigger another cutscene.