So I was reading the C5 notes and in it they mention hunting grounds labeled as "solo hunting grounds" where instant effect items might drop.
Seeing as how I am about to start leveling a new character on a new server I have a question... which are these hunting grounds? Are they specifically labeled? Is there a list?
There are no labels or defined boundaries you will ever see.
In general, 'solo' grounds are usually 1x hp mobs (or lower) and outside of 'dungeons'. Any exceptions seem to be of the 'not a solo area' type and not the other way around though. (Forbidden Gateway and Dragon Valley Pass for example.)
If your just starting a new character the only 'non-solo' areas you will see will likely be your 'starter dungeons'. (Cave of Trials, Elven Fortress, Elven Ruins, Mithril Mines, School of Dark Arts.)
The definition of solo hunting grounds is quite loose.
Mostly all Field type hunting grounds are designed for soloing. Unfortunately, it's not always the case. Many Cemetery and Dragon Valley mobs drop drop herbs, for example, even though the entire area is good for solo.
Generally you can guess x1 or x1/2 mob will drop herbs. Some (or all) undeads don't drop herbs. Also most x1+ group-type mobs don't drop herbs.
Other than that you can get herbs even inside some dungeons - from rare x1 mobs out there. For example, some robots inside Archaic Laboratory drop herbs.