由于 and 因为 — where each may stand

규칙 由于 and 因为 both give a cause, but they stand in different places:
由于 ONLY opens the first clause: 由于天气原因，航班取消了。
因为 may stand in either: 我没去，因为下雨了。 (由于 cannot go there)
由于 leans written and pairs with 因此; 因为 pairs with 所以.
因此 and 所以 mean the same; 因此 is the formal one and does not repeat the subject.