Imho a tag must categorise a content you need and you are looking for.
So vpn,webapp,apache,mysql, and much more like installation are good tags but i'm not sure concerning tag about levels (novice...middle and experimented.)
From my point of view any howto must reach the goal of the reader...even for a beguiner.
Of course jim it is only my 2c thought and if you need to add more tag....go. You can find all used tags in the help page and there http://wiki.nethserver.org/doku.php?id=category