How to erase/reformat HD and reinstall Mac OS?

I want to completely erase the hard drive on my MacBook and then
reinstall the Mac OSX (I'm currently on 10.8.2). The only instructions
I can find on the web - ALL the instructions I found - say basically
the same thing, which includes the step where you put "your OS DVD/CD
into the disk drive." Well, I don't have an OS disk. Haven't had one
for several years. The MacBook came with the OS already installed and
every update since then has been downloaded and installed from the web.
To my knowledge, there is no way to save an OS install disk via this
download process.

So, how would I completely erase/reformat the MacBook hard drive if
there is no OS disk?

I know this will be a no-brainer for some of you and I apologize in
advance for my lack of knowledge on this particular subject. I also
thank you in advance for any help you can extend.

If you must know why I'm planning to erase and reformat, it's because
the MacBook has started acting weird and I've tried a bunch of other
things to attempt to make it start acting normal again, with no luck.

As I said, thank you for any help you can give me.

8^)~~~~~~ Sue (remove x to email)
~~~~~~~~~

http://suzie-q-wacvet.com/
http://intergnat.com/malebashing/

 

http://support.apple.com/kb/PH11273