I would cite after every single quotation, paraphrase, and summary. If all the information in one paragraph is from one source, then the citation for any paraphrasing or summarizing could probably be done only once, but then that wouldn't be allowing for any of your own ideas that may be in that paragraph along with paraphrasing or summarizing other people's ideas. Whatever shows up in parentheses in the paragraphs, though, needs to be as brief as possible. (See below.)
Quotations need to be cited every time.
You need to have each source of information cited in TWO places:
1. the Works Cited page that is placed after the last page of your paper, and
2. in parentheses in the text of your paper, immediately after the quotation or paraphrase.
For example, this would go on the Works Cited page (with proper indentation for the second and following lines):
Du Bois, W.E.B. The Souls of Black Folk. Chicago, 1903. Project Bartleby. Ed. Steven van Leeuwen. Dec. 1995. Columbia U. 2 Dec. 2003
... and this would go immediately after the quotation or whatever:
The information in parentheses in the text needs to be as brief as possible. That's why there's a Works Cited page – for all the details of the listing.