To edit a dialog, you first need to enter editting mode by hitting the Edit Dialog hot key (The default setting for this is Shift-Command-E). Now you will be able to select and move and dialog item you wish. Arrow keys will allow you move selected dialog items as well. Holding down the command key will allow you to click and draw the window. Clicking in the bottom right corner of the dialog while the command key is down will allow you to resize the dialog (ie you could increase the size of the standard get and put dialogs). If you wish to resize items, you will need to set Dialog Editior's mode to programmer (this is the default setting). To exit the editting mode, hit command Q. You'll then be asked if you wish to save your changes. WARNING! Once you change something, you'll need to restore a saved version of the dialog to get it back.
If Dialog Editor cannot edit a dialog, it will beep (yes it should and will tell you why). If an error is encountered when saving the dialog, it will beep as well (yes it should and will tell you why).
If you resize a dialog that has a list of items, you'll should dismiss the dialog and bring it back up so that the dialog's code will handle the new size.