you must link every stock footage and transition with a sound effect - sound effects enhance the mood and the viewers experience.
the sound effects must be VERY subtle and barely noticeable - it should only enhance the viewing experience, not distract or be annoying. Be mindful of the volume.
:where to apply and compliment:
ask yourself: "Where can I apply sound effects in the video?" - you must apply sound effects to compliment seamless transitions, the stock footage and any other visual effects. All sounds applied must align / match up / synchronise with the visuals - it's very important that every element aligns / synchronises properly.
all stock footage must be "seamlessly" linked together in one form or another.
One of my favourite techniques is when editors manipulate time on a stock footage - when you manipulate time to either speed up or slow down footage - you give the viewer a new lens - creating a world that they have never seen before which enhances the viewers experience. For example - a time lapse of a flower / nature unfolding OR slowed down footage of a couple in love having a conversation or experiencing something. I expect you to apply the manipulation of time on all stock footage.