How do they do that?

I've come across some new blogs lately. A few of them get to review new products. The company sends them the product to review and they can do whatever they want with it. Most of them review it on their blog and then have a contest to give it away.

How do they do that? How would I go about getting some free products to review? I love free stuff and I'm not afraid to give my opinion. I would love to get some baby products, cleaning and household items, and cooking items. If anyone knows how I would do this, please let me know!