Robin Good: Here is a good guide providing the basic principles that should be followed when using, reposting, citing or quoting other people's content (both text and images).
The article outlines "proper methods of source attribution on the internet to guarantee the right people get credit for their hard work and ideas."
Specific sections of the article cover:
How To Cite Content in Blog Posts
How To Cite Content in Social Media
How to Give Credit to Guest Bloggers and Ghost Writers
How to Cite Images and Visual Content
Via Robin Good, Maggie Verster