I recently set up a custom domain for my Blogger blog and it was far more easier than I actually thought. It involved a change in DNS settings and then a change in my Blogger settings. The work around took 5-10 mins, the wait time was around 12 hrs and my domain was up and running.
I referred several online resources, but each failed to keep it simple. Here I would list some quick steps that will help a smooth transition to a new domain, without any downtime.
Since you are reading this, I assume, you've already bought a domain name with full DNS control. Now follow the steps below, in the same order as listed.
1) Log in to your Domain registrar's (DReg) site and check for "Manage DNS". This is where you will make the required changes to DNS. If you are not able to find "Manage DNS", your DReg could help you get there.
2) Once you are in the "Manage DNS" option, you will see some default entries. These would be pointing to a default host, defined by your Dreg. Ignore them they will not be required anymore.
3) There are 3 kind of records you can create here A, MX and CNAME. We'll just concentrate on A and CNAME for now.
4) You will now create 4 "A" records for your naked domain "example.com" and 1 "CNAME" record for your subdomain "www.example.com"
5) 4 "A" records will point to 4 different IPs -- 188.8.131.52, 184.108.40.206, 220.127.116.11, 18.104.22.168 and the "CNAME" record will point to "ghs.google.com".
6) In the "Manage DNS" system, you will see something like this:
Sub Domains for example.com
7) The additional entries apart from what you see above is not required. However confirm with your DReg before you delete them. These are the only changes required in the Dreg system. You can save your changes and exit.
8) It takes around 12 - 36 hrs for your changes to reflect across all DNS servers. So wait patiently.
9) Once you've waited for a day or so, log in to your Blogger account. Go to "Settings" > "Publishing". Click on "Custom Domain". As you've already purchsed a custom domain, go to Advanced settings. Here enter your custom domain like "www.example.com". Once you click Save, there is an additional option to redirect your naked domain "example.com" to your blog, dont forget to select it.
10) If everything goes well, your new domain should point to your Blogger blog. Incase it does not, you may have tried too soon. Wait for some more time and repeat the Blogger settings. It should be working fine then.
Pls note: There are several domain registrars and each may have a different approach to setting up a domain, but the basic concept remains same through out. If you get familiar with the above concept, you may put your queries to your Dreg in a more better manner. This may inturn reduce an unnecessary interaction time.