How can you judge a person to loan him/her the money?

Judging is one of the most difficult part. I mean what if we have judged someone wrong? or what if he/she  just made a Jackass out of us? The Question is how to judge ? Okay lets see I got a called From Lenny he requested me that he needs a $5000 loan from you. Okay! He is your friend you said okay buddy no worries , your money will be ready for you at my table , come at my house tomorrow and collect it. Haaaaa! He comes he says thank you so much and blahh bllahhhh! and then you ask him the real question that "Lenny! What time can you pay me back , because I am already short of little cash?"Lenny laughs innocently and says No worries dude I will return you back the sooner I can and then Bang! closes the door and never shows his hideous  face again. So now you know after three weeks that you have been  given a title of Jackass by Lenny. The sad part is that we got many people like Lenny roaming around the streets and in our friend circle. That now we don't  even feel to help the genuine person who is in need.