[linux-lvm] Understanding if a disk is partioned with LVM or not

[pent 5971]

Hi,
Im new to this LVM stuff and still couldnt read and understand enough.
But i have a RHEL 5x box (which i didnt installed) and we have
phsically added a new disk which i have to create a file system to be
able to use it.  df -h command gives normal /var /data / partions, but
id like ask how can i understand if the first disk/sytem is created
with LVM , and if so (any other box can be so in the future) what is
best way to add the disk and crete the file system?

Regards