A launch checklist should help a visitor complete the important tasks on your website. Start with what the site exists to do.
List the pages a first visitor will use and the action on each one. Test the navigation, one contact submission and any important downloads on a phone and a desktop. Check names, dates and the destination of buttons against the approved copy.
Assign someone to check the public website after launch. Record what should happen if a key feature fails and who can make a correction. Keep the checklist with the project so the team can reuse it for the next release.