The guide I'm posting will not only get you Ghost, it will get you completing the game in Low Chaos, NO kills at all, no upgrades at all and not alerting anyone.
Make sure the 2 boxes are ticked off at the end of each mission.
Save often in multiple save locations and make a save at the beginning of each level in case you don't get the boxes checked.
Also make sure you do everything as he does. In the second mission I think, I accidentally talked to the wrong person triggering a side quest, and when I failed that, it triggered an alarm so I had to redo the mission. It's at the very start of the mission before Samuel takes you to the city. If a girl talks to you at the top of the stairs, load the last checkpoint. ( actually there is a way to do it this way, but it's not covered in the video)
Posting the first video, the rest are in the side bar. He goes through the game really fast and I liked his commentary, you may not.