To choose the foreground color click on the eyedropper tool and make a selection or click once on the foreground color control. This brings up a dialog box that allows you to choose your own color. To select a background color click on the background color control and use the dialog box to choose a new color. To switch between background and foreground colors click on the arrow. The marquee is for rectangular or elliptical selections, the lasso is for freehand selections, and the magic wand is for selection of a similar color.
Every click doubles the magnification.
To reduce the display of your image hold down the option key and click. To clone, decide what part of the image you want to clone and take a sample of it by holding down the option key and clicking once. Move the cursor to the spot where you want the clone to appear, then click and drag to paint the clone. Everything outside of your selection will be deleted. The dodge tool lightens the image where you apply it, while the burn tool darkens it.