My pictures are coming out too dark - Cameras

There are four ways to make the image lighter
a) more light (flash, sun, etc)
b) slower shutter speed (allows more time for light to "expose" the sensor)
c) larger aperture (bigger hole = more light)
d) higher ISO (basically, amplify the available light more).

If you are using a point and shoot camera, the flash is usually only good for about 10 feet, so trying to get a good bright picture of subjects further away won't work.

Items b, c, and d are handled by the camera in automatic mode. In manual mode, set the iso has high as it can go. Set the aperture as large as it can go, and decrease the shutter speed.

Depending on the camera, you can enable the histogram to see if the images are too dark, usually by pressing the display button while taking pictures. If the histogram is off to the left edge, the picture will be too dark.

In post-processing, (e.g. photoshop), you can use Levels (control-shift-L for auto-levels) and it will move the histogram to the right, making the picture look brighter.