A great checklist from Six Revisions:

1. Have scalable web server resources
2. Get all of your social media accounts beforehand
3. Have content ready to publish for at least a month
4. Drop hints about the upcoming launch to build anticipation
5. Plan your tasks for at least a month after the site launch
6. Triple-check the technical details before going live
7. Launch on schedule
8. Contact your friends and family about the site launch
9. Provide easy ways of contacting you
10. Show site visitors a roadmap of what’s to come

Read further at the Sixrevisions.com blog.