Generally speaking, using the flash is the way out of this problem. Be sure you're close enough for the flash to be effective, which is usually within 15 feet (3 meters) of your subject.
Aside from the obvious uses in darkness, the flash can also actually help during the day! (Some people would even argue that this is the only acceptable use of the flash, but the final decision, as always, is up to you.) When you use the flash during the day, it's generally to bring out a dark subject against a light background. Flash used in this manner is called fill flash.
For instance, if you are taking a picture of your friend and she's standing in a shadow under an archway in the foreground, and behind her is a brilliantly lighted courtyard, then she will appear almost black against the background. By firing the flash, you can prevent this from happening.
The good news is that the light color of the flash (known technically as "color temperature") is pretty much the same as the sun, so it'll blend right in.
Another option is to force the flash to "off". The camera will try to compensate by making a longer exposure (or some other means), and you'll end up with a brighter scene overall. If the exposure is longer than 1/15th of second or so, you'll have to support the camera on something, or else your hand shake will cause the image to blur.