The beginning has to be what is EV on the dslr? It is the exposure value and the little button with the +/- does just that. Now if you read here I am a Nikon shooter so I will be using a Nikon configuration but almost all cameras have the same type of item on them.
EV as we will call it adds or removes light to the exposure settings of the camera you are using. One point here, if you shoot only on manual this is not for you. I shoot almost exclusively on manual but I do on occasion shoot on other settings which the EV button does work. You can set the amount of the EV for every setting like A, S, and P. You can change the EV using a couple of different methods. You need to check the manual for your particular camera as this is a general short article not an in depth lesson. You can see more examples on Studio 1 The Magazine or on one of the photo sites. The thing to remember is that you set the steps the EV uses to change the exposures. On the D700 the steps are 1/3, 1/2, or 1 step and is set on the Custom Shooting Menu B exposure. You change the image EV by holding down the button on the top of the camera and using the wheel on the back of the camera.
On the better cameras even though you set something you can override parts of it and use the EV separately. Try using it to help with higher shutter speeds with wide open lens to photograph birds in flight and use the EV to darken them instead of having them overexposed. Landscapes are a great place to us it also. Use a tripod and do HDR and use it to change things up a bit.
Go out and shoot and see how things work. Don’t forget to set the EV if your camera has a tendency to over or under expose on the default settings. You can look on line and see what the sites say about the cameras. My D300 or D700 are kept on a -0.3 so if they are shot on one of the non manual settings the camera is set to make the optimum image with its other setting.
The items that create the beautiful images you want are ISO, Aperture, Shutter Speed, DOF and White Balance which will all affect the images. These will be discussed in separate articles shortly or if you want more detail you can check on the Studio 1 The Magazine site for the articles which are being posted. They are being reorganized so they can be found easier.