The difficulty of such a task often surprises people, so don't feel bad.
There have been many threads here on the forums of photoshopgurus.com on this topic. Just Google { accurate selection cut out site
hotoshopgurus.com } and read through several of the threads.
You will find that the Magic Lasso is hardly ever the best tool for this. Tools with steeper learning curves are almost always the method of choice in the case of difficult cut-out situations. These include the pen tool (where the boundary is relatively smooth - eg, graphics, horizons without trees, etc.), and using channels as masks (where there are color differences between the foreground and background).
In addition, in complicated situations, rarely will one selection tool be adequate to achieve a good selection all the way around an object. Consider the case of a girl with frizzy hair with sky as the upper background, mottled light and dark trees as the background a bit lower down, and grass even further down in the image. This means that you have to know how to add to selections, subtract from selections, intersect selections, etc. to put together one complete selection all the way around the object to be cut out.
Finally, to avoid halos and other edge artifacts, you also need to be very familiar with feathering and anti-aliasing selections.
In summary, while some cut-out problems will be easy, in general, this can be one of the more difficult photoshop tasks one can take on.
Probably, the best way to proceede is for you to post one example image, and someone will be able to walk you through the steps for that particular case.
HTH,
Tom M
