The final play-style that you are awarded at the end of a level is dependent on the type of actions that you take while playing it. For each of these actions you earn points in one of the three categories, "Ghost", "Opportunist" and "Predator". The pie chart at the end shows the percentages of the points you earned in each category, and you are rated based on which category had a larger percentage.
You get points toward Ghost if you make it through the level without being detected, and without killing or performing knockouts . To get 100% you must also leave things more or less how you found them, no putting out lights, etc. Leaving doors open does not directly count against you. However if a NPC sees it opening or finds a door open that shouldn't be it might alert them, resulting in Opportunist points.
Each light that you extinguish gives you a small amount of points toward Opportunist.
Raising suspicions or being detected with give you a moderate amount of Opportunist points.
Knocking out citizens will earn a large number of points towards Predator.
Killing guards or civilians will get you a very large number of points toward Predator.
Knocking out guards will give you a moderate amount of both Opportunist and Predator points.
Strategies for obtaining your desired play-style rating:
- Remain undetected
- No kills
- Very few if any knockouts
- Only extinguish lights when you feel it is absolutely necessary
- Don't worry about raising suspicion, but try to not be detected so you can avoid combat and potential killing
- Extinguish lights as much as you want
- No kills
- Use knockouts sparingly
- Kill, and knockout indiscriminately until your heart is content.
The above conclusions are based on experiments I performed by running Chapter 1 a number of times while doing slightly different things. I first did a 100% Ghost run to establish a baseline. Each run after that I did almost the same thing but performed a certain kind of task once (extinguish a light, knockout a guard, kill a guard, etc). I took roughly the same path every time but there were variations, it is possible that what I did or didn't do (more/less stealth actions, etc) may have had a small influence on the final percentages but that variance should not be large. From what I have observed, it should not affect the results; you don't really seem to earn Ghost points, you instead start with 100% Ghost and loose Ghost percent by gaining percentage in the other categories. All tests were performed on "Rogue" difficulty to make things quick and more fool-proof, I don't know if difficulty level can influence the points awarded.