cPanel

The instructions below are written specifically for those accessing their site directories through cPanel. FTP user will need to adapt the instructions.

Before getting started - a note about modules
Modules available at Drupal.org are not guaranteed to work as described there, or even work at all.

It is very recommendable to read the "issues" page for any module you are considering installing to see what others are saying about the module and to be sure the version you are downloading is actually the right one for you. Sometime, unfortunately, it's not as simple as just picking the one which is "obviously labeled correctly". Some after-install tinkering is often required to get things working properly.

Finally, and above all - always make a backup before doing any work which will affect your database. If you have a backup there is virtually nothing you can do to mess things up which isn't reversible. If you don't have a backup, there's a lot you can do to make your site irreversibly messed up. :)