You can't choose to do a "viral" campaign or video. You can do a campaign or a video and HOPE it goes viral, but viral isn't up to you. It's up to the audience and it's incredibly, incredibly rare. It means that people are excited enough about it to bug their friends with it. And those friends feel the same way. Viral is an Okay Go video that gets three million views in three days. You see it in your Facebook feed posted by fifteen different people. Plus two cousins and an aunt email it to you. THAT is viral. But you can't build a marketing plan around something going viral any more than you can plan your retirement strategy around hitting the Powerball. So make great content, post in places that having sharing tools, but expect modest results. Then build off of them. And if one day you wake up and you have 10,000,000 views, you are waaaaaay ahead of the game.