Quality, in this case, really refers to the suitability of your source for your academic research. Generally, you want academic sources, but even newspaper articles might be appropriate depending on your need.
Think critically - We all evaluate the trustworthyness of advertizing, billboards, news shows, and other information every day. The same critical-thinking that goes into deciding what ads to trust goes into deciding what articles to use.
Think in terms of of your source's sources, intended audience, language and where it is published.
Bowdoin college site detailing the process of writing an academic paper from generating ideas to writing and editing papers. Although focused on papers in the History field, this information can be applied to many fields.