Another useful tool for making selections is the Magnetic Lasso tool. When this one was introduced, it quickly became one of my favourites. I like it most because it seemingly snaps to the edge detail within an image, allowing me to select objects with ease. How does it work so well? Here's the secret to using the tool effectively.
It all has to do with edges.
What are edges? Edges are differences in contrast. (This is also how sharpening works - driving edge detail away from each other ...) You can use the Contrast box to help Photoshop determine if the edge will be included in calculating the path of the Lasso. So it's really important to pay attention to this adjustment, especially if you are trying to get a selection out of some subtle detail.
If you are using the Magnetic Lasso tool, and your paths look jagged or don't seem to be following the line that you see in the image ... make the adjustment in the Contrast box. A little fine tuning goes a long way towards great results.