Just a few of the free tutorials at the Writing Academy
Clichés and Their Place in Prose
Passive and Active Voice
What Are Narrative Tenses And Why They’re Important
Correct Quotation Mark Usage
He Said, She Said: Dialog Tags And Using Them Effectively
The Show Versus Tell Debate
How To Write A Great Critique
What Are Comma Splices
An introduction to Advanced Haiku
Using Third-Person Multiple POV
Common Screenplay Mistakes
How to Format a Novel Manuscript
How to Format a Screenplay
How to Format a Short Story Manuscript
Correct Colon Usage
Correct Semicolon Usage
I didn’t check the individual links, so I don’t know if they explain things well, but they’re at least a good start to understanding some of this.