Here is overview of the steps:

1. Your current domain name should be registered on Google’s Webmaster Tools. If it is not, then the notification will probably not help and you should just stick to the 301 Redirects.
2. Add your new domain name to Google’s Webmaster Tools and go through the verification process.
3. Once you have both sites registered, click on the old site to bring up the Dashboard. On the left menu, click Site Configuration -> Change of Address.
4. Select your new domain name that you want to use from the drop down and submit the request.

Is There Going to be a Penalty for Changing my Domain Name?
Google isn’t very clear on that so you are at the mercy of Google once you change your domain name. Generally it is not good practice to change your domain name, especially if it is a site that earns income (or if it is a client’s site). I recently did a domain name change for my own site (this site). I didn’t have much to lose and was willing to accept a temporary loss in traffic.

When would I use a 301 Redirect?
One reason is to redirect your current domain name to a new domain name. If you changed your domain name for example. It could also be used for redirecting individual pages if a page has moved and you want to redirect old links to a new page. Today we just talk about updating your site to use a new domain name.

How do I redirect my old domain name to a new domain in Linux/Unix
1. Ideally you should make a copy of your existing site. Either on a new hosting account or as a new domain on your existing account (if your host allows it). When both sites (old and new) are set up and working individually with their own domain names, you can proceed to redirect your old domain name to your new domain name.
2. Create a .htaccess file in the root directory of your old website. You can also create the file on your own computer first than ftp it in. If using Windows, you could name it “htaccess” then rename it “.htaccess” from your ftp program after you upload.
3. Copy and paste this code into that file, changing the “www.yourdomain.com” text to your new domain name:
   Options +FollowSymLinks
   RewriteEngine on
   RewriteRule ^(.*)$ http://www.yourdomain.com/$1 [R=301,L]
4. That is all there is to it, it immediately goes into effect. You can test it by opening a new browser and typing in any link to your old site. It should redirect to the same page on your new site. If it does not, check to ensure that you added a period in front of the .htaccess file

How do I redirect my old domain name to a new domain in IIS (Internet Information Server) on Windows?
You will probably need to talk to your host to determine the best method. If you have admin access to your server you can do this:

1. Right click the folder or website you want to redirect and click Properties.
2. On the Home Directory (or Virtual Directory) tab, click the “A redirection to a URL” option.
3. Enter the domain name or page you want to redirect to.
4. Check the “A permanent redirection for this resource” option.
5. Save by clicking OK. Then test by opening a new browser and going to an old link. It should redirect to the new domain.

Redirecting a Domain Name in IIS

Additional Resources:
Google recommends using 301 redirects if changing the domain name of your existing site to get the best results in their index.