How to know a Writer is good or not?

[Dopani]

I'm going to hire some writers write articles for me. I thought will find them via forums, fiverr or freelancer but how to know quality articles that they can provide me are good or not, also know them as good writers?

Any advice

 

[scopio]

You can ask them to write a topic, they will send you samples for comparing, evaluating
Their field experience and field you require, they have correlation?