I have worked for several years in information security. That is, protecting yourself from viruses, online identity theft, etc. And there are some things that are pretty simple, but will make a big difference to how likely it is that something bad will happen to you. I have made a couple of presentations which are worth sharing with friends.
Security Hygiene - three simple steps to better security
LastPass - Why password managers matter, and how they work.
Each of these PDFs is short (presented in 5-7 minutes), but this is a case where forcing a time limit has meant only the most important points stay in.