If you want to preview your new domain before going live by setting the nameservers, there is a pretty easy way to do this.
You need to edit your "hosts" file on your computer.
On Windows systems (7 and 8) the hosts file is found at
c:\windows\system32\drivers\etc\hosts
Be advised that you may need to allow viewing of hidden system files.
Edit that file in notepad (or Notepad++) AS ADMINISTRATOR.
Add the line as follows:
<server_ip_here> <domainnamehere> www.<domainnamehere>
(Replace <server_ip_here> with the IP address of the web server, and replace <domainnamehere> with the new domain name you want to preview.
Once saved, restart the web browser and there you go!
More info and details can be found here
http://www.howtogeek.com/howto/27350/beginner-geek-how-to-edit-your-hosts-file/