Checklist for launching a site

Note: This is for Drupal 7, see also Drupal 10 version.

When a site is made live, it faces a variety of new performance, user interaction, security, maintenance, and quality assurance concerns. Every site is different, but this checklist will get you started with common site launch tasks. It will also get you thinking about the kind of tasks that may be needed for your specific site's needs.

Performance

Go to Site Configuration -> Performance and within the Cache area enable Cache pages for anonymous users and Cache blocks by clicking in the checkbox if necessary. You should see checks appear.
Within Bandwidth Optimization enable Compress cached pages, Aggregate and compress CSS files, and Aggregate JavaScript files.
Turn off unnecessary modules, such as Devel.

User Interaction

Protect your forms against spam and attacks.

What kind of forms are anonymous and authenticated users able to access on your site?
Have you enabled CAPTCHA, reCAPTCHA, Honeypot, or an anti-spam service?
Be sure that all publicly exposed email addresses are protected from spam bots with solutions like Obfuscate Email or a custom obfuscator.

Email: Verify that the site email address in /admin/config/system/site-information is not a test address. Also verify email addresses in other modules that send notifications, and verify the text of email messages your site generates.
Index your site for search at search settings and test.

Domain

Check if one of the domain redirect options is enabled in the .htaccess file. Either redirect URLs without www. or vice versa.
Web Services

Update API keys for modules that make use of them, such as Twitter, or Google Apps.

Security

Check that your admin passwords are secure.
Upgrade Drupal Core and Contrib modules to the latest version.
Turn off on-screen error reporting at admin/config/development/logging. (admin/settings/error-reporting for Drupal 6)
On the Permissions page, verify what permissions anonymous and authenticated users have been given.
On the User Settings page, verify that account creation settings are as you intend (can users create their own accounts, and do they need approval?).
Check Reports > Status report and make sure there are no warnings or errors.

Backups and Maintenance

Cron - If cron is not running, your database will get bloated.
Backups - Regular database backups are essential. Check out the Backing up and migrating section for more information.
Statistics - You'll want to monitor your site going forward. Do you plan to use Drupal core statistics, or have you set up another service such as Google Analytics?
Check Reports > Recent log entries for errors and warnings, such as missing files or URLs. Check that there are no red flags in Status Report.