Everything depends on what software you want to install and the type of websites which you'll host.
You should install an OS which is also compatible with the control panel you plan to use. Then you should install Apache, MySQL, PHP, Perl, etc. - everything depends on the requirements of the website(s).
I assume you're running the server at home. A 6Mb connection is not enough for a server unless you'll only host a small website. This is not recommended if you plan to jump in the web hosting business, please search for similar threads if you want to know the reason why it won't work. You should send the server in a data center.