There are a few key commands used with this tool that you absolutely must learn. Write them down and practice practice practice until this becomes habit.
Practice with the following keys as you make selections. BUT... do NOT let go of the mouse until you are done. Once you do, your selection is set and you can’t change it. All you can do is deselect and try again.
To deselect, go to your menu bar under SELECT/DESELECT. Try to learn the shortcut for this one. You will use it a lot!
Notice that when you make a selection, you start at one corner of an imaginary box around what your trying to select and drag to the opposite corner. There will be times when selecting from the center out is more desirable. Try holding down your OPTION/ALT key while making a selection. That key lets you draw from the center out.
Next, make a selection and try holding the SHIFT key. This one forces your rectangle to be a perfect square. Your oval, will make a perfect circle.
NOTE; This is a pretty universal trick. Just about any computer program that has a circle or square tool will react the same with the shift key. This is also known as “constraining” an image. We will go over this again later when it comes time to resize an image without squashing it.
Finally, if you make a selection and it’s just not quite on target, hold your SPACEBAR and move the entire selection. Let go of the space bar and you may continue to adjust your selection shape or size.
OPTION/ALT lets you make a selection from the center out.
SHIFT forces, or constrains your selection to perfect square, or circle.
SPACE BAR lets you move your selection around.
Again, you must be holding the mouse button down until your selection is right where you want it. Then, and remember this, let go of the mouse first. Then your keys.