Learn English – to be certain to do something versus to be certain of doing something

Did you remember locking the door?

This question is being asked now (moment A) about whether you remembered some time in the past (moment B) if you locked the door some time further back in the past (moment C).

Did you remember to lock the door?

This question is being asked now (moment A) about whether you remembered some time in the past (moment C) to lock the door some time slightly in moment C's future (moment B).

While there's an element of the future in the second sentence, both sentences refer to events in the past of now (moment A).

The difference between "on leaving" on the one hand and "by selling" and "in trying" on the other hand is easy: "on leaving" is to do with time and means "when you saw him", whereas "by selling" and "in trying" are to do with the cause and effect relationship. But there is a difference: by = she sells insurance in order to earn a living, it is her aim, it is a means to an end; in = Howard does not try to protect the Queen in order to put his own life in danger, it is just an occupational hazard for bodyguards, a side effect.