熟人 An acquaintance, a person one knows well. Its opposite is 生人, a stranger, literally a “raw person.”
靠谱 Reliable, trustworthy. Said of a person who does things in a sensible way.
拉关系 To pull connections. To make friends with someone one barely knows, for a purpose.
走后门 To go through the back door. To get things done through improper private connections.
在家靠父母，出门靠朋友 At home, rely on parents. Away from home, rely on friends.