Assuming you have two new hard disks each 250 GB /dev/sdb and /dev/sdc. Say you wanted to mount this LVM to your home folder.
Create Physical Volumes
Create a Volume Group
vgcreate lvm01 /dev/sdb /dev/sdc
Create a Logical Volume
lvcreate -L 500 GB -n my_lvm_name lvm01
Note: you may have to play around with the -L option until you find the correct one. It may be 460 or 480. Make sure to maximize your size. You can always 'lvremove my_lvm_name' and try again.
Then label it
e2label /dev/lvm01/my_lvm_name /home.
Then add the entry to your /etc/fstab file. Instead of listing the device with the path /dev/lvm01/my_lvm_name, just use LABEL=/home.
Later on if your /home folder gets full you can buy another hard disk /dev/sdd and add it by doing
vgextend lvm01 /dev/sdd