Delete stuff: click near items to remove
The Delete Tool is the best way to remove peices from your design that you no longer want. Either that or quit everything and start again.
To use the Delete Tool, click the red cross on the Drop-Down Menu, or press control while clicking.
To gain precision when deleting objects, Zoom In, this way you are less likely to accidently get rid of the wrong part.
You cannot delete Goal Objects, but why would you want to?