A move goes wrong in predictable ways. Doing it in this order avoids all of them.
1. Set the site up here first, before touching DNS
Copy the files and the database across and get the site working on our server while the live site carries on where it is. You can view it here before the domain moves by editing your local hosts file – see Accessing a website by changing your local hosts file. Nothing is at risk at this stage because no visitor is affected.
2. Check it properly
Not just the home page. Check a few inner pages, the admin login, any contact or checkout form, and the images. Confirm the PHP version here suits the site and that the extensions it needs are enabled.
3. Lower your DNS TTL first
A day or two before the move, reduce the TTL on your DNS records so the change propagates quickly. If you leave the TTL at a day, some visitors will still be sent to the old server a day after you switch.
4. Freeze, sync, switch
Stop making changes on the old site. Copy across anything that has changed since your first copy – usually the database and any new uploads. Then change the nameservers or the A record.
5. Leave the old site running
Do not cancel the old hosting for at least a week. While DNS settles, some visitors will still reach the old server, and if anything is wrong you want the ability to point back.
6. Afterwards
Once traffic is arriving here, confirm the certificate has been issued for the domain, and check the site address settings are on https.
We can do the whole move for you – ask before you place the order, as it is often included.