Live in a bubble. Do the opposite of everything Liz tells you to do.

Seriously, there is NO simple magic way to avoid getting sick. Avoiding sick people -- fine, only often they're spreading the illness before any symptoms show up. Washing the hands -- great, IF you use soap and water and wash for at least 30 seconds (and use a clean towel to dry on). You might also want to avoid touching doorknobs, as they are great places to pick up germs and virii. Also avoid public places, don't use chairs others have used, and in general, live in a bubble.

You can keep yourself as fit and healthy as possible -- but you're NEVER going to avoid getting sick.

Sorry to be the one to break it to you.