Read the iphone manual; that's a feature they added to make it easy to get to.
I just want to you to know that the person was saying that you have to press the home button quickly, then press it again longer to get to the search. I tried it while I was in messages and it DID work, but I don't think they intended it to work *that way*, however, if you're already on the first home screen and tap home once, it will bring you to spotlight... I know that's a feature. The way he was saying it, it didn't sound like he was at the home screen already.