First of all, choose a picture. 

 

1) On your Photoshop toolbar, select the eraser tool and hold your mouse down until 3 different erasers emerge. Select the 3rd one - which should be "Magic Eraser Tool".

2) Then, like you would have filled a background with color, click on the background once. The background should disappear immediately (despite possibly a few bits requiring you to clean up).

3) It should probably look like that after you click it for once, and continue until all the background is cut out. Here is the result of the example:

As long as the background color is not too similar to the object of the image you would like to keep, then this method would actually work quite well.

If you are cutting out a photo, I suggest you use the other eraser tool - called the Background Eraser Tool. It's the second option down the list when you hold on the eraser icon. It does not help you cut out the background as efficiently as the 3rd does, but it does help you greatly. Try it and discover for yourself!