You could to a couple of things.
Wi-Fi: Wi-Fi consumes power even if you are not using its features to connect to a network. You can turn it off to save power. Go to Settings > General > Network > Wi-Fi.
Backlight: Setting the backlight to “always on” will significantly reduce your battery life. Only use the backlight when necessary.
Equalizer: Adding EQs to playback uses more of your iPod processor, since they aren’t encoded in the song. Turn EQ off if you don’t use it. If, however, you’ve added EQ to tracks in iTunes, you’ll need to set EQ to “flat” in order to have the effect of “off,” because iPod keeps your iTunes settings intact.
Minimize use of third-party applications: Excessive use of applications on iPod touch, such as games that prevent the screen from dimming or shutting off, can reduce battery life.
Fetch new data less frequently: Applications on iPod touch such as Mail can be set to fetch data wirelessly at specific intervals. The more frequently email or other data is fetched, the quicker your battery may drain. To fetch new data manually, from the Home screen choose Settings > Fetch New Data and tap Manually. To increase the fetch interval, go to Settings > Fetch New Data and tap Hourly. Note that this is a global setting and applies to all applications that do not support push services.
Turn off push mail: If you have a push mail account on iPod touch such as Yahoo!, MobileMe, or Microsoft Exchange, turn off push mail when you don’t need it. Go to Settings > Fetch New Data and set Push to Off. Messages sent to your push email accounts will now be received on your iPod touch based on the global Fetch setting rather than as they arrive.