Short Tutorial on Citing Sources
If you're using footnotes, you have to adopt a style and keep with it. If you're not footnoting, you need to give resource name, author if appropriate, and page number.
What sources can you quote, you can choose your limitations. In general, you can quote short pieces from magazines and newspapers, make sure to give date of publication in these cases (example: Jan-Mar or June 23, 2014, depending on how often it is published and the name of the author, if given).
What constitutes a sources. Almost anything, except Wikipedia and other sources like it. Wikipedia has sources listed, which you can search to find the original source for the piece you want to add to your publication, but since it is an open source document, which anyone can add to that means misinformation can easily be given. So, in general, it is frowned upon to quote citing Wikipedia as the source. You can, as I said, find the original source and quote from that. Wikipedia is a great source to read and gain the knowledge you might need on a particular topic. I know that sounds like an oxymoron, but I'm just passing on the fact that Wikipedia is not a respected source. So, if you choose to quote and cite Wikipedia, get ready for the push back from your readers.
If you go to a lecture, you can quote giving credit to the person doing the lecture. I would normally cite this as name, lecture place and date. If you do an interview with someone, you can cite this by just giving the name.
When to use footnotes? I would use footnotes for an academic or industry paper, such as a thesis or white paper. Books that are of a high level and intended as research, I would use footnotes and list resources at the back of the book giving all the details of each quote.
If you copy info and paste a section of text from some source into your document,and then rewrite it, you do not have to give credit provided you used this copy mostly for mental inspiration and to remind you what points you want to make.