Fixing a Problem Organization Chart
I tried creating an organization chart for the first time, and it's a real mess. Do I have to delete the entire slide?
No, just delete the organization chart itself. From there, you can begin again. If you see a Content placeholder, click the Insert SmartArt button. If you see nothing, click the SmartArt button on the Insert tab of the ribbon. In each case, the Choose a SmartArt Graphic dialog box appears.
Expanding Diagram Choices
I can't create the graphic I want with the SmartArt choices.
Remember that you can apply style options in the Shape Styles and Shape Effects galleries. If those options aren't enough, you can create a diagram yourself from the shapes in the Insert tab of the ribbon. You can also manually design an illustration with PowerPoint's drawing tools. As a last resort, create your diagram in another program (such as Visio, SmartDraw, or Illustrator) and then insert it.
Also, Microsoft has allowed third-party providers to create more SmartArt graphics. In time, this will mean that there will be tons of new SmartArt graphics, and you might even get a particular style created for yourself.