Hello everyone,
What is the best technique to extract image from its background using photoshop. I just don’t get that crisp fine edges
or finishing. Also how to master selection tools like magic wand and other lasso tools , it is so difficult to use this tools
to perfection.
Practice…and patience.
You will learn that there really is no ‘right’ way of doing it. It will be different for every image. Sometimes the wand works, other times select color. However, sometimes you just have to suck it up and manually lasso the thing. You can also make a path and marquee it in order to have nice continuity around the edges. There really is no trick to the wand though, just getting to know how the tolerance works (which comes with practice)
Use the pen tool + paths. Easily modifiable, scalable. Easy to make selections or masks from. Pen tool just takes a long time to master.
I usually just use the polygon lasso tool. Zoom way in and trace away! Feathering your selection a few pixels helps relieve the hard edges you may not want.
There are some other neat techniques if you need to select something fine like hair. Do a Google search for “Photoshop selecting hair.” I like the techniques using channels such as: http://www.designertoday.com/Tutorials/Photoshop/4387/Selecting.Hair.Adobe.Photoshop.CS3.Tutorial.aspx
I use the triangular lasso tool and the hard eraser tool. It gives me great results.
If you are working on scanned pencil or pen sketches. I find it very useful to copy the sketch in a new layer and then select multiply or darken in the layer-mode…
Then you can color you sketch and put the sketch on top. You’ll have nice black lines…And even smoothing along the edges. without using the wands or selections tools… and as someone mentioned…what do you want…extract a person from a very busy background. Then you’ ll need a combo of tools. And Combo’s are best mastered through practice and failure I’m affraid. That is the nice thing about photoshop. You can do anything in infinitive ways 
I was going to type a good technique in here but there are great tutorials on the subject online:
Hope it helps.