Switching your network mode to GSM instead of dual mode will always make a difference (as its not searching for a 3G signal which I believe is a big drain). But obviously you might not want to do this
Also having bluetooth not on obviously makes a difference.
Having your 'packet data' setting on 'When needed' and not on 'When available'.
Having your display brightness turned down.
Having the backlight go off after 10 seconds instead of 30 which mine seemed to be defaulted to.
Having the basic date/time screen saver kick in after 20 seconds or so rather than whatever its on.