Make sure that you are logged in as root and that no other user is logged in, then follow these steps;

1) fdisk /dev/sdb -- create a partition
2) mkfs.ext3 /dev/sdb1 -- format the partition as ext3
3) e2label /dev/sdb1 somelabel -- set a label 'somelabel' to the partition.
4) echo "LABEL=somelabel /home ext3 defaults,noatime 1 2" >>/etc/fstab -- auto mount at bootup
5) mount /dev/sdb1 /mnt -- mount somewhere now
6) cp -pPrfv /home/* /mnt/ -- copy everything over preserving everything
7) umount /mnt -- unmount it

// keep the old data in the original location for now
8) mkdir /oldhome
9) mv /home/* /oldhome/

10) mount -a

Now check to see if everything works. If it does (it should), then do the next step:
11) rm -rf /oldhome