Wiping MacBook Clean

So I got a new MacBook Pro yesterday and I am going to send in my old MacBook Pro to the company Apple uses to recycle laptops. Before I send it in though, I want to wipe the old laptop clean of everything. How do I go about that? I can't seem to find the CD I could use to basically re-install the operation system. Any other way to do this?

Thanks.

Remove the hard drive from the old MBP and place it in a USB carrier or use an adapter. Attach it to your new MBP, run Disk Utility, wipe it clean using at least a single secure pass. (I recommend 3 times.) Put it back in the old MBP and ship it off to Apple.