Imo, the most important technique (besides standard ajax with js lib of choice) is making use of hashchange and organizing your behavior into 'routes' based on the hash. You'll notice that Gmail does this -- it has URIs ending with #inbox, #label/action, etc.

Using hash routes allows you to keep track of state and decouple event handlers that set state from code that updates the page. Plus you get back button functionality and bookmark support.

Some background info on hashchange: http://blog.whatwg.org/this-week-in-html-5-episode-3

jquery library for dealing directly with hashchange: http://benalman.com/projects/jquery-bbq-plugin/

Higher-level jquery library for handling hashchange: http://code.quirkey.com/sammy/ . It has more assumptions and imposes more constraints on the structure of your code. But in return you get route parsing and a DSL.

If you go through the examples/tutorials in those two libraries you should gain enough knowledge to get started.