I’m not a pro or whatever but this is how I do it, using 2 methods. I mostly use the first one but with pratice and some focus, the second method brings a better result.
A. Method one :
Select the pen tool
Zoom in.
Click all over the object to cut
Right Click “Define a selection”
Make sure to have the image’s layer selected
Ctrl+C then Ctrl+V.
Your cut is now in a new layer.
B. Method 2 :
Instead of following the edges of your object to cut, click at the “peak of the curves”, making straight lines.
Click on the pen tool and switch it to “outil conversion de point”
Using that tool, click each point and turn it until your lines follow your objects’ curves. (sorry my example is #fail)
Once it’s done repeat the first method’s steps from “Right Click “Define a selection”