if you use rpm packages (and not compile programs yourself), simply use the rpm erase command (you'll have to be root if you haven't made any magic):
# rpm -e programname
above "programname" is the name of the program you wish to uninstall (like "gaim" without the quotes, for example, if you wish to remove it). the "su" command gives you superuser rights, so you'll need to type in root password for that (it's not displayed when you write it).
alternative method is to use sudo instead of su (you do not become root, like above, but the command is run as root) - this works only if the user you are logged in as is allowed to use sudo:
$ sudo rpm -e packagename
after that command you are asked your password (password of the user you _currently_ use, not root's!). if you are allowed to sudo, then it works - if you are not, the command fails and you need to use the above method. I'd advice you to use sudo.