I tried to make my introduction pretty interesting, saving all of the boring stuff for the literature review, etc :-)
I think I started with a quote (despite this being a little cliché) and talked about how that succinctly introduced the ethical questions raised by the technology I was researching. I wrote about debate surrounding the topic and briefly mentioned the different areas I was going to cover. Basically I posed a lot of questions that I planned to answer in the rest of the essay!