What is the best way to launch a website to make it go viral?

You have no control over whether or not a website, or anything, goes viral. Going viral is a phenomena where something gets insanely popular for (usually) no apparent reason. Anyone advertising a product/service/website hopes their ad and product go viral but it happening is out of their control. It's more a freak occurance then a created result.

How you get traffic to your website will vary on the website and its target audience. Without knowing that it's hard to give specific recommendations. But some generalizations that you may wish to try include:

• Search advertising (Adwords) - If the genre your site is in is very competitive avoid the common search terms and go for long tail searches. Your costs will be lower and your ads will be even better targeted and result in a higher conversion rate.
• Paid advertising on related websites - Putting a text or banner ad on a related website will promote your site to your target audience. If you advertise on a popular website this can drive a lot of traffic to your site and may be less costly then Adwords.-
• Participate in forums and communities related to your topic. Do not spam them. Participate as a regular contributer and be sure to put your website in your signature. Assuming you are a regular participant and offer good contributions the other members will be likely to visit your link. (digitalpoint.com forums got started this way by participating at sitepoint.com forums).-
• Comment on related blogs - Similar to above but you comment on related blogs. Once again, do not spam them and offer good contributions.-
• Attempt to get a related website to review your website and publish the results on their website - This basically amounts to free advertising assuming your website is good and they review it as such.

Directory submissions should be done but they won't really drive any traffic to your website. Using social networks can be done as well, but don't expect too much from them either (but definitely have a twitter account so you can follow any talk about your website).

And, as always, be patient. Sites don't get popular overnight. It takes time to get the word out and build up a following. Good websites are eventually rewarded with good traffic.

For a website to go viral it will help if you tick a few boxes in the human psyche.

1. Is the site easy to use? If the user has to think about how to use it, they won't tell anyone about it. Make sure the site is accessible.

2. Does the user get a sense of satisfaction from using the site? If the user doesn't feel good using the site, they won't tell anyone else about it.

3. Is there a compelling reason for them to come back to the site? If the user has got all they need from the site in one visit, they will not bookmark it and will then forget it.

4. Is it easy for them to spread the word? Don't expect anyone to go out of their way to tell anyone else about the site. Why would they want other to know about the site? Is it easy for them to tweet / blog / talk about what your site does? Is it clear what the site is about?

There's an interesting service called LaunchRock that you can use as a "landing page" to help your pre-launch site go viral. (see it in action)

It provides a signup page for you that visitors can drop their email into to be notified when you go live.

If you combine this with some word of mouth advertizing, tweet about it on Twitter, share it on Facebook, Google+, LinkedIn (if business related) etc. you should be able to attract some interest.

It is also handy if you have a 1-liner story about your site so users know what they are signing up for: e.g. "The best social TV geolocation sharing site - coming soon"(*)

Also consider providing additional incentive to sign up early - e.g. special treatment/discount offers of some kind if you sign up before date X.

Finally, when you do go live, you'll be able to broadcast your launch to many people - which depending on the social interaction required for your sites success... may be very helpful... if you need that "Critical Mass" to get conversations off the ground.

Even if you don't use the LaunchRock service, I'd recommend rolling your own signup page before launch.

(*) ok, totally made up buzzword fluff but you get the point.

Note: I have no affiliation with LaunchRock (or the sample site using it), but I too am hoping to use the service to launch my own site.