How do I access Stylistic Sets in Adobe Illustrator.
For example this font. Which I have installed has Stylistic sets: http://www.myfonts.com/fonts/debi-sementelli/cantoni/
This could vary quite considerably depending on the version of Illustrator you're using. In Illustrator CS6 (I'm afraid that I don't have other versions with which to test), you can access your OpenType Stylistic Alternates by;
Here you should see numerous options - many of which may or may not be available, depending on your font - but amongst which are 'Stylistic Alternates', 'Swash' and 'Contextual Alternates', etc.
If you want to view the various characters (rather than switching settings), you might more usefully go to WINDOW > TYPE > GLYPHS. You can then use the 'Show' dropdown box to see a visual grid of all the characters the font provides.
Hope that helps.