Has to be revisited
Only sketches and storyboards exist, not specified yet.
Story
Whenever I use an asset, I actually use a rendition of that asset. Selecting a rendition is easy. I can find assets by entering tags, by identifying pages they've been used on or by browsing a folder hierarchy - what is available for my search depends on how and where the asset is stored. When I've found the asset I've been looking for, I can choose one of its renditions to add it to the page. This rendition is then linked to the page and made visible during rendering as well as when previewing or editing the page.
If no rendition fits, I can just edit the rendition which is closest to what I need - if that's permitted, that is. A simple editor allows me to do common tasks such as cropping an image, connecting two movies using a transition, or rearrange and delete the pages of a PDF document. (1)
A third method for adding an asset to a page is by directly uploading it. Uploading an asset may physically attach and link it to the page. More likely though, it will add it to one of the configured asset sets. That's great because I can add new assets directly during editing and using them creates a rendition for me on-the-fly. During upload, I may have to choose a folder to store the asset under or to assign existing or new tags to it - that really depends on the asset set the template designer has chosen as upload location. I don't really care, I just provide what's requested.
(1) I don't know and actually don't have to know, if editing the rendition really edits it - and thus changes it everywhere it's being used besides on my page - or whether Magnolia first creates a new rendition based on my edits. This is something that's only of interest to our brand management.