I think what makes a effective introduction to any article not just a Wikipedia. is if it starts of talking about the subject or giving a simple definition or talking about where it happened or what happened so the reader isn't lost on the topic. the reader might still not know much but the reader will have a start to help him and her. then you start to go into more what you wanna talk about and the main ideas you will have in the paper and why you want to talk about it. i think that's a good way to start off with a good introduction.