Google Scholar is a very useful tool to focus on academic sources. This video tutorial explains the basic use (replace kingston university library where it explains about search settings):
And you can learn how to utilise search engines (like scholar) more effectively to refine your search.
This guide (from UCBerkeley) provides good suggestions about evaluating websites as sources.
Reading academic papers is a skill you can develop (and will also help you write better). Check here and here for useful ideas (or if you prefer to watch videos instead of reading...)
About the difference between scholarly sources and general articles.
Evaluating sources is part of a broader issue of coping with data. The title of this University of Washington course says it all: Calling Bullshit: Data Reasoning for the Digital Age
Breaking a topic down is often a useful way of discussing it. But not every list is a useful categorisation:
Electronic Dance Music
Trap
Dubstep
Electro House
Deep House
Trance
Drum and Bass
Progressive
Film Music
Chromatic Harmony
Leitmotifs
Melodic Contour
Augmented Chords
Audio-visual Synchronisations
Orchestral Strings
Diegetic
Steven Pinker explains good writing:
An extensive resource about academic writing from the university of Toronto
On the difference between analysis and description
And a PLOS editorial about structuring papers.