I will tell you certain lessons I had learned by experience.
I submit these for your consideration, please.

1. Never trust a stranger on the outset.
2.Remember a saying `Treat any new guy you come across as a scoundral.. it is up to him to prove otherewise!`
3.Help only those who really need it.
4.You may help the helpless just because they need it but the circumstances do not allow them to seek help. In all other cases,help only when help is sought.otherwise,your help will prove redundant.

5.Set clear terms for any transaction.