We suggest that you refer to your organization’s or professor’s citation guidelines for how to specifically cite sources from websites like BibleGateway.com. For example, Calvin College uses KnightCite, which walks students through the citation process:

Here are the websites for the most common style guides:
APA: http://apastyle.apa.org/
MLA: http://www.mla.org/style
Chicago: http://www.chicagomanualofstyle.org/home.html
 
...and a few more from universities with additional guidelines:
http://www.lib.washington.edu/research/wri.html
http://library.duke.edu/research/citing/
http://owl.english.purdue.edu/owl/resource/560/01/
 
Here are some tools that provide automated citation help:
http://www.bibme.org/
http://www.easybib.com/