These days there is not much to do for a website relaunch once the owner is happy with the touch & feel on a stage system. But the following things sure make a difference:
- Google Analytics: Make sure the old Google Analytics code is running on the new system upon launching.
- Redirects: Make sure, the old URLs are properly redirected to the new ones. Also make sure that the sitemap.xml of the new website is available and still registered with Google Webmaster Tools / Search Console.
- SSL: Make sure that your webmaster has access to your SSL certificates and configures them to take advantage of secure HTTP (HTTPS).
- Email Gateway Provider: If you have email forms on your website you want them to deliver form submissions to you in a safe and reliable way. Make sure your webmaster uses a solid email gateway provider (such as mailchimp mandril or sparkpost) and has your sending domain verified and set a valid email address as the sender.
- If you use Google Maps on your website make sure your webmaster whitelists the new domain in the Google API Console. Otherwise your Google Maps might not work.
- It would be good to set speaking page titles and descriptions for each page. This is relevant for search engine result pages.