Be brief, but provide enough information that your audience can track down the source.
Highlight what is most important criteria for that source.
Include who/what and when.
According to Professor Jane Smith at Stanford University....(abbreviated verbal citation)
When I interviewed college instructor John Doe and observed his English 101 class...
Jason Hammersmith, a journalist with the Dallas Times, describes in his February 13, 2016 article.... (Full verbal citation)
Full verbal citations include all the information about the source thereby allowing the source to be easily found.
ex. According to Harvard University professors, Dr. Smith and Dr. Jones research on this topic published in the Summer 2015 issue of the New England Journal of Medicine....
Abbreviated verbal citations include less information about the source, but still includes the most important aspects of that specific source.
ex. A 2015 study in the New England Journal of Medicine reports that Harvard University professors....
It is a easier for a listening audience to understand that what they hear next is coming from that source.
Introduce the quote (ex "And I quote" or "As Dr. Smith stated"...) PAUSE. Start quotation. PAUSE at the end of the quotation.
Introduce the quote. Say QUOTE. Start quotation. Say END QUOTE.
2018 NSDA Informative Speech Champion Lily Indie's "Nobody puts Baby in a closet" has examples of verbal citations. Listen to two verbal citations starting at the 5:30 mark and running until 6:50 mark in this YouTube video.