De Introdução ao Microsoft Office PowerPoint 2007 :
To create multi-level bulleted lists, type in the text lines as usual. Click at the start of any lines that you wish to appear as a lower level list then press the Tab key from the keyboard. The selected lines will receive an additional indent and will get a different bullet symbol. Using the Backspace key produces the opposite effect.
To change the bullet symbols used, first click in one text line of the list level that you wish to change. Next, click the down arrow to the right of the bulleted list button in the Paragraph group on the Home tab. Choose a bullet design from the displayed collection.
To choose a different button, click the Bullets and Numbering option, then in the dialog box that appears, click the Customize button.