Pro tip: first change the nameservers, then wait a few days and then remove the domain name from the account (or deactivate the account).
That way, you can decide what content is shown while DNS caches around the world are slowly moving over to your new hosting. If you delete the domain first, those people see an account suspended page or a parking page. If the domain is still assigned to your active account, you can keep showing your website on it, or show a page saying your site is under maintenance. Once you remove the domain, you lose that ability.