What is the best way to isolate a person/item in Photoshop?
There isnt a single best method to Isolate Objects in Photoshop
The recommended approach is a combination of the pen tool, layer Masks and Extract.
The Pen Tool & Masks
The Pen Tool works best when you have large-resolution Images that have smooth curves or simpler, more geometric figures. It gets hard to use around organic objects and areas like flowing hair or leaves on a tree.
Here is a videos of the Pen tool in action, it’s part of the hilarious ‘You Suck at Photoshop’ series by Donnie Hoyle. See the rest here.
And a surprisingly good tutorial from about.com on – Removing the Background with Photoshop Pen Tool
Some Free Pen Tool Practice Templates that you can download and trace to sharpen your pen tool skills
The Extract Filter
The Extract Filter, can be found in your Filters Menu [not in Filter Gallery]. Its useful for more organic areas like hair and leaves where there are too many edges to trace with the pen tool.
I could explain the process setp by step, but theres a great video on youtube that takes you through all the options and is easy to follow.
More videos from this series can be found at www.TutVid.com
There are many ways to extract using photoshop but do yourself a favor and follow these tips.
Garbage In = Garbage out: Start with high-res Images, they will let you zoom deeper and make precise paths vs guessing where the aliased pixels end.
Pick subjects with strong contrast: The Contrast helps distinguish it from the background and makes the extract process easier.
Non-Destructive Editing: Dont use the Eraser, use Masks with Smart Objects so you can always revert back to a previous stage and try a different process, especially with the extract filter. It will take some trial and Error.