Very roughly....
A train is 'due' when it is about to arrive.
Money is 'due' when it is owing to someone.
In (almost) all other cases, 'do' is the verb for an action "Did you do your...
Due to [ preposition ] is followed by a modified or unmodified noun, to make a phrase. e.g. Due to the complexity of the problem, ... Because [ conjunction ] is used to introduce a subordinate...
(Diligence : effort, care, undertaking, responsibility)"He applied himself to his job with diligence, and was rewarded with promotions and pay raises on a regular basis.""Operating a nuclear reactor...
EXAMPLE:The sudden chill she felt on her neck was due to the window being open.BETTER:She felt a sudden chill on her neck, because the window was open.