You are:
Sherlock Holmes.
Each line of the riddle refers to a word that can be made by adding a prefix to —ook. The first letters of the particular answers for each line spell my name, see below.
When I silenced them, they trembled!
Shook — Sh! means Silence!
When five joined me, they sang praises.
Hymnbook — Five suggests V or maybe the fifth letter, E, but I can't make anything with that, so I guess five just means five letters.
After my decline halted early, my tales could be shared with people around the world,
and be sent where they could never have gone before.
e-Book — Ebb is to decline and it ends early, so the prefix is Eb.
Right before me was a castle.
Rook — R is for right and the rook is the castle in Chess.
With just a first glance, I could truly see.
Look — This must be look, but the first glance would be G. Not quite sure how this works.
An awkward oaf gave me a whole new perspective on life -
Outlook — The "awkward oaf" is an anagram of "lout".
A sea lay before me, and I was stirred - inflamed - ready to be transformed -
ready for life's next seasons - prepared to taste all life had to to offer! ...
Cook — The "sea" is a C, of course.
Which path should I follow? king? or madman?
Kook — K for King gives a madman.
One hand before a second, and I found my guide, but -
Handbook — "Hand" plus the second letter of the alphabet, B.
His drunken paramour led me to miss what I should have seen.
Overlook — the "drunken paramour" is an anagram of "lover".
Before I cry in distress, let me review the precedents.
Law-book — to "cry in distress" is an anagram of "bawl".
I follow my lead, for I am incompetent!
Mook — "my lead" means the first letter of "my".
It lets me see. After an hour, I might let it chain me up...
Eye hook — The eye lets me see plus H for hour.
Can me, like a fish.
Snook — A can is a tin and the chemical symbol for tin is Sn, which gives us this Caribbean fish.
All answers together give:
Shook Hymnbook E-Book Rook Look Outlook Cook Kook
Handbook Overlook Law-book Mook Eye hook Snook
Finally, the title:
Sherlock Holmes is the "King of Detectives", but also an eccentric. "Follow the clues" hints at mystery stories.
