I was working on a site that needed SSL setup for credit card form submission.
SSL ( Secure Socket Layer) is a protocol that allows data to be encrypted when transmitted from the browser to the server.

Setting up SSL on the server requires a certificate to be installed. I usually buy the certificate from godaddy. 

On some sites, you will see only certain pages redirect the page (URL) from http to https. I personally prefer to have https on the entire website and the best way to set it is on the server’s .htaccess file for the following reasons:

1- You don’t have to deal with changing your scripts or adding extra html or php redirect.

2- If you have to test the script on your local machine or on a server that isn’t SSL enabled, you don’t need to make changes to it.

3- It more secure.

Adding the following server redirects should do it. Just save the following in .htaccess under your root directory:

RewriteEngine On
RewriteCond %{HTTPS} !on
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

You can learn more about it here: http://en.wikipedia.org/wiki/Https. Wikipedia explains the process in simple “plain english”.