I'm going to use Unbounce to generate my contest landing pages and variations.

Step 1: Create and account or sign in.

Step 2: Create a new landing page, choose the "Viral Social Media Contest Page"

Step 3: Customize the contest messaging, and image

Step 4: Save this version, and visit your landing page dashboard to publish the page.

You may want to point your page to a custom subdomain, if so you can follow this tutorial by Unbounce.

It's different for every major hosting providers, but Unbounce does a great job of providing the neccessary info.