With all the features digital cameras have these years, you may find the duration of the battery is too short. This could well be your biggest expense, but there are some things you can do to lengthen the time your batteries stay charged. Let's start by listing the three largest "drains" of power.
The LCD screen consumes the most power. Turn this feature off unless you really feel the need for it. Using the camera's viewfinder will help you to conserve your battery power. The flash is another big power drainer. Whenever you can, use natural lighting to take your photos and switch off the flash. This will save your battery power for the times when you absolutely need the flash. A third drain on your battery is use your zoom constantly. Zooming in and out consumes more power than maintaing your focus in the same position. Try to find a setting you like and stick with it as far as possible. More... / Hide...
Some other things you can do to make your battery power last longer:
The need to purchase more or recharge your batteries is something you won't be able to avoid completely, but with a few precautions this won't be needed as often.