UK domains are looked after by Nominet. Each reseller (like 123-reg) has what is known as an IPS tag (123-reg uses HOSTEUROPE). You can see this by doing a whois search on a .uk domain (http://www.geektools.com/whois.php).
US domains (.com .net .org) may be looked after via any number of registrars. For example 123-reg uses one called OpenSRS, another is NetworkSolutions (actually owned by Verisign) who confusingly also sell direct to the public.
UK domains can be easily transferred by changing the IPS tag associated with it, it is also wise to change the email address associated with the domain to one you have access to. US and other TLDs need their administrative email address changing to something you have access to before they can be transfered.
To move a domain into (for example) 123-reg, change the email addresses and (if applicable) IPS tag. The go into your control panel and choose “Transfer domains to 123-reg”. Enter the domain and (if it’s a UK domain it will be checked for the correct IPS tag) a transfer request will be dispatched to the current admin contact (which should be you).
In reality it’s never this easy :) Usually this is down to the fact that the email address listed for the domain has not been changed or is inaccessible. Usually a reseller will change a domain on receipt of a fax signed by the original owner as proof of identity. Nominet also provide a service for .uk domains which (for a fee of £15+VAT) will change the details on a domain. This can be useful if an ISP has gone bust.
Many companies charge rather extortionate fees for transferring domains away from their systems. Continuing the examples 123-reg allows you to transfer a domain to another 123-reg user with ease. Simply go into the control panel for the domain and choose the “Transfer to another 123-reg user”.
When you register a domain, and are setting up the hosting you will need an external dns or secondary dns – especially so when you have your own server.
In the past GraniteCanyon.com and secondary.org have been good providors of this service, for free.
Solving DNS Issues
If you’re not sure why your DNS isn’t working or are having problems you should definitely try putting the domain or host in question into an online checker like DNS Report or CheckDNS
If you get random errors on your site, or some people can’t see it when you can, check that all your DNS servers are giving the same answers using Squish DNS traversal check.
Domain Name Servers
Domain Name Servers (DNS) are the Internet’s equivalent of a phone book. They maintain a directory of domain names and translate them to Internet Protocol (IP) addresses. More information here
The Key to DNS
The main thing to remember about DNS and domain names is that these things take time to populate round the Internet and it may be 48 hours before things update for you. The main thing to do is make sure you have all the settings and configurations as you want them (double check even!) and then sit back and wait. The only way to make transfers happen any quicker is a time machine, the only way to make DNS propagation any quicker is to have your own DNS server and tinker (beware!) with TTLs and the like.
You can check that your site is working in its new location before the DNS changes have propagated. On Un*x/Linux edit /etc/hosts and add a line with the new IP address, a space, and then the hostname. On Windows do the same to C: /Windows/System32/Drivers/etc/hosts (don’t ask why MS thought this was a good place to put it!). You machine will use these entries to convert the hostname into an IP address before asking DNS to do the job. Don’t forget to remove the line a few days later once the DNS entries have propagated.