Q:

Repartition my existing hard disk

First time Mac user here.
I'm quite aware with all the posts here about repartitioning hard disk but I'm quite confused if repartitioning would erase all my data on my hard disk.
I recently bought my Mac and it was pre-installed with Lion, and my hard disk size is 750GB, and under in one partition only.  I would like to divide the disk into at least 2 partitions where I can put my music files so that it would be easier to backup with any backup/imaging software.
With my current setup, it means that I have a recovery partition on my disk that would allow me to reinstall Lion if problems would occur.
If it would erase all existing data on the disk if I repartition it, then my only choice is to do this:
1) Backup first my data using Time Machine
2) Boot from the recovery partition and erase and partition (3) the hard disk
3) Restore the image to the disk to the desire partition
What do you guys think?

A:

Make sure to back up all of your data first, just in case.
Next, create a USB Recovery HD (at least 1GB) with these Apple forum instructions:

Create a USB thumb drive Recovery HD using the Lion Recovery Disk
  Assistant. Download this and install it. Then, insert a thumb drive
  and create your bootable Recovery HD. Last, boot from the USB thumb
  drive and from inside the Recovery HD on that, try the resize.

You should be able to resize your main partition after booting from the USB Recovery HD.
Another option is to use the Recovery HD on your Mac, as noted in the solution that @bmike suggested in another question - boot to your Recovery HD and use Disk Utility there to resize.
The solution that you've mentioned will work, but is a bit more work.

