All actors have properties, which are accessed using the properties window. You can open the properties window of an actor by right-clicking on that actor and choosing "Properties" from the context menu, or (in most cases) by double-clicking on that actor (remember that you have to select brush wireframes to do this, not a surface--but you shouldn't be modifying brush properties anyway). Properties are divided into sets, the primary ones of which are outlined below. There are also several kinds of properties: