How to Punctuate Extracts Correctly...?

Hi sirs & madams,

Could somebody on this forum point me in the direction of a style manual (or online resource/website) that deals specifically with how to punctuate extracted quotes/content in normal prose.

I have grasped that it's quite common to set the quote aside using a colon:

"Like so..."

But I've also come across different, perhaps more unconventional, ways of punctuating the above--e.g., where the writer doesn't use a colon but instead treats the whole quote as if it was a noun as part of a continuous sentence, as in:

Blah blah blan end of parapgraph.

"Quoted material"

is the reason why we have blah.

Schematically, it reads as though the quote above is taking the normal position of the sentence's "subject", and there's no use of a colon.

Apologise for rambling on a little, and thanks to anyone who can help me out!

Sean