Turn off anything you don't need - wifi, Bluetooth, even go into Airplane mode if you don't expect phone calls. (Don't worry about location, though - GPS uses almost no battery unless an app asks for location.) Keep the screen off as much as possible (30 second timeout at the longest), and keep the brightness down. Don't charge the battery above 80% or discharge it below 40% if possible.
(Don't worry about apps in RAM - if they're just sitting there without running, they aren't using power. Constantly "clearing" or "cleaning" RAM is one of the biggest wastes of power.)