It is tempting to tag every note with a several tags. However, I broke myself of that habit once I realized that Evernote indexes every word in every note. So if you have a great quote on “purpose,” for example, you don’t need to tag the note with “purpose,” so long as the word appears in the note. This only adds more clutter. The key is to remember that less is more.
I don’t see a need for the tags in my workflow, but I use them to of caution. I add a few to each note in the event at a later date I want them. It’s easier to add them as the notes are created than to add them years down the road when you have a need for them.