How to cite a conference paper or conference proceeding varies depending on how the paper/proceeding was made available and the style manual required by each journal or discipline. There is no such thing as a separate style guide just for conference papers.
Typically, if a researcher is citing something from a conference, it is a specific paper or presentation rather than the entire conference proceeding.
CSE, ACS, APA, IEEE, and Chicago Manual of Style all give instructions for how to cite conference papers. All of them agree on some basic principles:
If the paper is published in a journal, cite it as a journal article
If the paper is published in a book, cite it similar to a book chapter
If citing the whole proceeding, cite it similar to a book
If the proceeding has a unique title, include that as well as the name of the conference.
All style manuals vary on specific details to include when citing an unpublished conference paper or presentation; unfortunately, very few style manuals include the conference name and location if published as a book or a journal article.
Differences for specific style manuals
ACS Style – does not include the title of the paper itself or the page numbers.
APA – uses only author initials, not full names – only the first word in the title is capitalized (unless it includes proper nouns)
Chicago Manual of Style – the main differences from APA are that the title of the presentation/paper is given in “quotes” – the title words are all capitalized properly – and the author names are spelled out in full rather than abbreviated.
Book chapter format (ACS Style Guide, 3rd ed., 2006, p.307-309):
Garrone, E.; Ugliengo, P. In Structure and Reactivity of Surfaces, Proceedings of the European Conference, Trieste, Italy, Sept 13-20, 1988; Zecchina, A., Cost, G., Morterra, C., Eds.; Elsevier: Amsterdam, 1988.
Book chapter format (Publication Manual of the American Psychological Association, 6th Ed., 2009, section 7.04):
Morrison, R. S., Cronin, G. M., Hemsworth, P. H. (2011, November). Sow housing in Australia – current Australian welfare research and future directions. In R. J. van Barneveld (Ed.), Manipulating pig production XIII (pp.219-238). Proceedings of the Thirteenth Biennial Conference of the Australasian Pig Science Association (APSA), Adelaide, Australia. Werribee. Australia: Australian Pig Science Association.
Unpublished presentation (Publication Manual of the American Psychological Association, 6th Ed., 2009, section 7.04):
Liu, S. (2005, May). Defending against business crises with the help of intelligent agent based early warning solutions. Paper presented at the Seventh International Conference on Enterprise Information Systems, Miami, FL. Abstract retrieved from http://www.iceis.org/iceis2005/abstracts_2005.htm
Unpublished presentation (Chicago Manual of Style, 16th edition, 2009, 14.226):
Valle, Jose J. and John R. Eyler. “An FT-ICR Free Electron Laser User Facility for Determination of IRMPD Spectra of Gas-Phase Ions.” Paper presented at the 51st ASMS Conference on Mass Spectrometry and Allied Topics, Montreal, Canada, June 8-12, 2003.