public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}

routes.MapRoute(
"ShortAbout",
"About",
new { controller = "Home", action="About" }
);

routes.MapRoute(
"ActionOnly", 
"{action}/{id}", 
new { controller = "Home", action = "About", id = UrlParameter.Optional }
);

routes.MapRoute(
"ActionOnly", 
"{action}/{id}", 
new { controller = "Home", action = "Index", id = UrlParameter.Optional }, 
new { action = "About|Index" }
);