What is your best strategy when doing viral marketing?
I suggest you remember it’s not marketing that makes something go “viral”. You can’t force it to happen but you can aid people in spreading the word.
Results generated from “viral marketing” are not going to stay for a time long. I think patience and hard work will do a good job in promoting your site. However, there are some tools and softwares but you must read their reviews before using them. I haven’t tried them yet 
You don’t “do” viral marketing. You can improve your chances of a clip or blog going viral by using popular and/or “hot” items and launching supporting comments/posts on as many relevant sites as fast as you can, but that is about it. If a subject is doesn’t lend itself, it won’t go viral no matter what you do.
Two suggested approaches:
People like funny things that make them laugh. Think about what you would be likely to share with your closest friends and then try to convert your own content/product into that format.
If you’re not funny, then try to be extremely useful. Sites like Make use of dot com are extraordinarily useful and their content is virally shared.
And lastly, mix that all up with a good reputation and it will be even more likely to be shared.
Community participation increases viral marketing. The more people you interact with, you will spread the word better. Also forums and guest blogs are examples of viral marketing.
Viral marketing needs not just a lot of effort but a number of people to be effective. The question now is how to attract a lot of people to make your marketing go viral. One way is to promote free promotional products or render free services.
Messenger, message and environment are key factors for viral marketing