Great question, Agin.

Depending on the situation, you may want to ask for references. Perhaps ask friends or associates who they would recommend.

Without being more specific about the situation you may be facing, I'll give it a shot.

I'll give you a take from my company's stand point. If we don't know, like, or trust a business person, we don't do business with them. We work at growing the relationship to the point where all three of those have been satisfied.

For example, when a person wants to join one of our referral clubs, we check two business references and have an interview to make sure there isn't a conflict with any other member, and determine if is felt they would be a good contributing member. We typically have a one-to-one to get to know more about them and their business, and help build that know like and trust factor. 

When we feel the applicant is a good fit, they are welcomed.

On the other side of that coin, if the new applicant can't or won't follow our training or instructions, or they show themselves as a bad person to do business with, we counsel first, then remove them from the club. (Honestly, the bad members will show themselves quickly.)

I had a handyman years ago that made two appointments to do work for me. Both times I was stood up without a call or excuse. I couldn't take the risk of referring him to anyone. I felt as if the same lack of respect would be shown to people and clients I cared about. After counselling, he moved on.

I hope this helps.
Todd