Gamersyndrome: Get as much experience as you can and you will be able to unlock most skills in the game as soon as possible.
via N4G: pc news feed http://n4g.com/news/1232230/tomb-raider-skills-guide-pistol-expert
via N4G: pc news feed http://n4g.com/news/1232230/tomb-raider-skills-guide-pistol-expert