The process of creating a graphic design work will depends on the technical skills in use of many tools that available on the interface photoshop software. You must really understand the characteristics of all the tools are provided in photoshop. It will make the design process more effective and can produce any professional design works. Lack of understanding in use the tools will bring the major problem in the process of casting any design idea that you want to create.
The picture above is the analogy how to crop the image object for the purpose to separate it from the background that may we do not want. In the process of cropping the image object, photoshop provides any variety of tools, you simply choose which one that you thing useful for any purpose in the process to create your design works. The above analogy is how to use the tool that allow you to make the path that use to make selection that look natural and soft. Therefor I prefer to use the one of the tool in photoshop, that is Pen Tool (P). Surely you have to understand the characteristics of the Pen Tool (P) and how to use it.
The first step is open any picture that you want to change the background, and then select the Pen Tool (P) that will used to cut any part of the image that is not expexted. For more details, Ok let's see the picture above. Pen Tool (P) has the ability to follow the edge of the image object in detail. Here you must practice to use and play the flexibility of Pen Tool as shown like the picture above.
Once you have completed to make the path curves of the image object with the Pen Tool (P), you still allowed to reform the path in some other part of the image object. After all has already done you must convert or change the path curve to be the selection of the image object by pressing Ctrl + Click on layer path on the pallet path. Look at the picture above! the next, press Shift + F6 button on the keyboard will show the feather radius value that allow you to adjust itin order to make the result in cutting the edge of the object image more soft. Select the layer image, to remove the background area, press Ctrl + Shift + I selection will select to the background that you want to remove it and by press the Delete button on the keyboard.
Once the background was removed you are free to replace it with another background as you wish. This is a little method but most commonly used to make any graphic design works! Have a try!