Suggested character build - Physical 5, Intelligence 5, Focus 5, Charisma 3, Determination 3, Speech 3 and the rest 1. While levelling, concentrate on Physical or Focus statistic. You can get more XP by observe and investigate desk in addition to work. At morning, spend time talking to co-workers. You can start your work at afternoon (you finish faster if you have high Focus). Try to get your boss, Nathan as ally as soon as possible.
The skeletons re-spawn. Most of my time spending killing those skeletons. Quite monotony. Much fun if the skeletons don't re-spawn so I can concentrate on puzzle stuff more.