There are three main settings you'll need to get to grips with if you want to make the most of your camera; Shutter Speed, Aperture and ISO. You will also need to learn how they affect one another to get the perfect exposure.
If you need to get up to speed with the settings on their own have a quick read of my previous posts on the basics:
To take a well exposed picture you need to ensure that the right amount of light falls onto your image sensor. To start with you need to work out which is the most important setting to concentrate on.
1/80 sec; f/22; ISO 500
For this image I wanted the depth of field to be quite wide, this was to ensure that only Dylan and Millie were both in focus. To ensure this happened I started with a small aperture (high aperture value) of f/22. As the aperture wasn't allowing much light to fall onto the sensor I had to have a low shutter speed of 1/80 so that the light was being let through for long enough. I had the ISO on 500 as I have found this to be a good value for overcast, bright days when shooting outdoors.
Final Settings: 1/80 sec; f/22; ISO 500
1/6400 sec; f/5.6; ISO 2500
For this image I wanted to freeze Millie despite the fact that she was in motion. For this I put the shutter speed up to 1/6400 as I have found this to be a good value when I've been shooting agility I thought it would do well in this image. This fast shutter speed doesn't let much light fall onto the sensor so I had to make sure the other settings would compensate for this. I also wanted to ensure that Millie was in focus so I put the aperture value at f/5.6, if I had it any lower there is a chance that she might have not been in focus as I could not be 100% sure exactly where she would run past me. As these settings were more fixed to get a good exposure I had to play with the ISO more. It was a dull overcast day with not much natural light so I ended up on 2500.
Final Settings: 1/6400 sec; f/5.6; ISO 2500
1/250 sec; f/2.5; ISO 200
For this picture I wanted to ensure there was no noise on the image so I needed a low ISO value. As I had a good amount of available light I set it to 200. To ensure that I could keep the ISO low with the available light I kept the aperture open with a setting of f/2.5 to let enough light in. I then ended up with a shutter speed of 1/250.
Final Settings: 1/250 sec; f/2.5; ISO 200
Capturing an image is all about how much light is falling onto the camera's sensor. To get the correct exposure you need to work each setting with each other. I find it easier to play with the shutter speed and the aperture depending on what outcome you are looking for in the image and to set the ISO more in line with the ambient light levels you have.
If you have a shallow depth of field this will allow the camera to have more light fall on the sensor so you may need a higher shutter speed to ensure that it isn't falling on the sensor for too long.
If you are shooting in a dark area you may need a higher ISO to compensate for the low light levels.
As most people are shooting with digital cameras now it's much easier to learn the theory and then play around to see how your images come out and learn by trial and error. I find that I learn a lot quicker by doing things and seeing how they turn out. Digital is great as you have instant feedback from what you have just done.