Then tell me where and how to choose and buy?

I wonder how they determine the quality of CBD oil. I'm looking on the Internet, now you can safely buy the CBD Oil. It is not forbidden and free to access. I read that heals many diseases and generally useful to have it at home. Decided to find out how to distinguish between them is CBD Oil. I look there and different manufacturers and much more. The question is, have you already bought CBD Oil? You can tell which one is better. What and where to buy that would not be deceived? I would like to find more information on this issue. If you know. Then tell me where and how to choose and buy?