Hold Alt with lasso tool to remove unwanted area from the lasso selection
So Hold Shift while doing lasso to select more complex object by adding more area to the selection.
Lasso close its gap as soon as the mouse release.
Why use Lasso Tool?
Lasso Tool allow us to isolate portion of image for later image editing. When portion of image is selected, it can be apply filter effect, cut and paste into new layer, move, transform and painted independantly from the rest of the image. Unlike Marquee Selection, Lasso tool give more flexibility on selection image area of any shape.
To access the Lasso Tool, Press L. By default it will select Lasso Tool, press Shift+L again it will loop in Polygonal and Magnetic Lasso Tool. You can also access these tools from Tools Palette.
It is strongly recommend you to own a tablet while working with lasso tool, in fact many of the Photoshop tool require tablet to work efficiently. A digital drawing tablet such as Wacom is a great choice.
Draw around the object you want to select. Some complex object might not be able to completely cover by lasso tool in one stroke, you can always stop and continue lasso the remaining area. Don't worry about the lasso accidently covered the unwanted area, because you can always go back and remove it easily.
When the object is too complex to be lasso in one stroke. You can release the mouse and continue the lasso. To continue your lasso hold Shift and your lasso cursor will include a plus(+) sign, continue to lasso the remaining part and repeat until you cover everything you want to select.
If you want to remove portion of image from existing lasso selection, hold Alt and then draw the lasso surrounding the area you want to remove.
Unlike the regular Lasso tool, instead of dragging, you click and release the mouse button at the corner of the object you want to select.
To select Polygonal Lasso Tool, press L and then press Shift+L until you get the Polygonal Lasso tool. Start from corner and click every corner you encounter until you reach the first point you clicked to close the selection. Note that you can also double-click to let Photoshop automatically closes the selection from the point you double clicked to your starting point.
This is one of the cool tool provided by Photoshop. It analyze the colors of the pixels between the objects in the image and the it try to snaps to the edge of the nearest object as if the edge of the object is pulling your lasso selection.
Magnetic Lasso Tool performs best in a image that has high contrast between objects in the image. For Example the armor in the image against its background.
Click on the edge of the object you want to select, then simply move your cursor around the object without clicking. You can click certain point of the object to force the line lay on that location, if the Magnetic Lasso tool adds a point where you don't want, press backspace to delete one point backward.