perspectives, initialize/display/position

Determine the initial perspective:

public class ApplicationWorkbenchAdvisor extends WorkbenchAdvisor {
   public String getInitialWindowPerspectiveId() {
      return MyPerspective.ID;
   }
}

Display the perspective-selection and determine position:

public class ApplicationWorkbenchWindowAdvisor extends WorkbenchWindowAdvisor {
   @Override
   public WorkbenchWindowAdvisor createWorkbenchWindowAdvisor(
      // ...
      configurer.setShowPerspectiveBar(true);
   }
   @Override
   public void preWindowOpen() {
      // ...
      // determine the position (here, at the top on the right):
      PlatformUI.getPreferenceStore().setDefault(IWorkbenchPreferenceConstants.DOCK_PERSPECTIVE_BAR,
                                                 IWorkbenchPreferenceConstants.TOP_RIGHT);  
   }
}

see also: Views, ordered in several registers (with tabs)