Are you aiming your presentation at students, or more for staff to help them help students.
Either way, I tend to prefer to make the focus more of good academic practice, so more "What to do" - rather than "what not to do".
However, the points I'd probably include are:
1: Intro / activity- probably trying to find out what students think plagiarism is, rather than telling them what it is (e.g. using Twitter / Mentimeter / whatever to find out what your users currently think.
1a: Have a ready prepared list of what you think they'll say & also the types of things that you think they might forget about (e.g. inventing data!)
Then I might move on to good practice, including as well as the obvious (take notes; use bibliographic toosl to help you etc) things that students don't see as plagiarism directly (e.g. time / essay planning, so you have the time to do it well & don't panic at the end!)
Tools: Assuming your students are allowed to see their similarity reports on Turnitin - I might then start to help them understand how the reports work - Steve Bentley's "SImilarity Sim" is really good for that, as they have to think about them rather than you telling them what to think. e.g. http://eprints.hud.ac.uk/id/eprint/30172/
Then I might mention other tools that you have in your institution to help students.
Above all, I'd aim for it to be interactive and get the students involved as much as possible & probably do it in more than one sessions, as academic integrity is such a bit topic!