How Do I Find Out Who Owns A Domain Name?

I want to buy a certain domain name to put up a website. The domain name isn’t used, but it unavailable. How do i find out who owns it?

What Should Expect To Pay For A Domain Name That Another Company Owns And Is Willing To Sell?

I own a company and the domain name is already taken and used by another company that only uses it to redirect people to there main site. So they dont even need it. I contacted them and they are willing to sell me the domain name. She told me to make her an offer and I am trying to figure out a ballpark figure to offer her. Please be realistic. Thanks.