Whether you've made a selection by Photoshop tools or used a plug-in you'd want your selection to look nice and smooth on a new background. If the edges of the selected image were not softened or feathered during the process of selection you may shade them in Photoshop.
To do that open Select menu and choose Feather
Click to enlarge
In the opening dialogue window type in a number of pixels to be feathered (2-5 are usually enough)
Now you can copy your selection, paste it into a new environment and evaluate the result
No feathering
Feather 5px
Feather 15px
Feather 50px
More Tutorials: 
