A Few Questions about PR/Giveaways & Such

I have began wondering about how some of these Blogs I read approached the concept of Giveaways a PR stuff. Can you tell I am not even sure what I am talking about. I am wondering did you just contact the company and say "Hey"? Were you approached by the companies? And if so how? Did you start our blogging for personal stuff and then fall into givaways and reviews?

I guess I am just trying to figure out some stuff-I am interested in possibly doing reviews and such but have no clue if it is right for our family or how to go about doing it.

I have a million questions such as what made you decide to do it? Has anyone ever reviewed a product and wrote a less than shining review?

I have posted a few posts that are sortof along the lines of reviews but really it is just my personal feelings and wanted to share. If anyone reads this post and maybe can give me a heads up in understanding this whole concept that would be great.

Please keep in mind that I am just curious at the moment and full of questions. I honestly am not even sure anyone reads this blog so more than likely I am just typing to myself (which might be along the lines of a mental condition-ya know like talking to yourself, I do that too)

Thanks in advance if anyone responds I truly appreciate it.