Let us start by enabling the use of .htaccess for you server (usually this is turned off by default). You have to set the AllowOverride to All from None in the Apache configuration file (placed in /etc/httpd/ or /etc/apache2/ usually). Follow this post on Ubuntu Forum if you need more help.
Now let us start with some simple redirects. Unlike mod_rewrite, the redirects done by .htaccess are visible on the client's address bar. Assuming that you would like to redirect http://abc.com/old.html to http://abc.com/new.html, write the following rule in your .htaccess file: