How to know which software is correct?

I am using
Quote:

[root@localhost sbin]# uname -a
'Linux localhost.localdomain 2.6.32-220.el6.i686 #1 SMP Tue Dec 6 16:15:40 GMT 2011 i686 i686 i386 GNU/Linux

I want to install an vlc software as well as some other softwares on my system (on centos-6.2).
when I googled to find out the softwares their is big list is comes on their side like(rpmforge.com ,etc)
When I download the software and I try to install it on system by using yum or rpm it is not installed on my system it gives me errors.
I dont no which software is to download from the list will you plese help me to get out this problem.

A package has prerequisite packages. What are those error messages?