Our Go Booklet is most complete description of how to play Go on this site. It's presented here in 5 sections:PDF version (3.66 MB)  is available (updated 2010).
Here is a single page Quick Ref  produced for the UK Go Challenge.
There are some slight differences in the rules used in different countries around the world, however for almost all practical purposes (more than 99.999% of games) they produce the same result.
The BGA has adopted American Go Association-style rules for use in tournaments, as opposed to Japanese rules previously. Please see our policy page Rules of Go  for the full details.
For a comparison between the various rules sets see our Rules Comparison  page.
Some other sites which also present the rules of Go in English are:
For links to rule sites in foreign languages see our Foreign Links  page.
The Rules of General Graph Go  are how a mathematician may see Go.
The rules of the events of the various British championships are in the British Championship  section.
Here are the rules of Lightning Go Tournaments  used in the Netherlands.