KimD wrote:
Clues and general advice:
Try to learn their history--it sounds like a cliche, but past behavior can tell you a lot about future behavior. If someone has done some really immature, irresponsible, or unethical things in their recent past (and if they're an adult), don't expect them to suddenly snap out of it. Like ladyelaine said, if someone is close with a real gossip-monger--the truly hurtful, judgmental, socially manipulative kind--it's likely that they are too. Nasty habits and behavior can be contagious.
I think it takes time; get to know someone slowly. Don't expose your more personal information right away, don't make yourself vulnerable, until you feel more comfortable. Don't let infatuation mislead you. Conversely, know that a bad first impression may also be misleading, at least sometimes.
Not everyone is a real back-stabber, but everyone does have their moments, like little white lies they may tell you because they don't want to hurt your feelings, or to be polite. (I know that can hurt anyway, but the intentions behind that sort of thing are often rooted in compassion...an important trait in a friend, obviously!) They may even say something that is/seems unkind about another friend behind their backs, but it may be because they want to express some frustration or confusion, or try to understand why someone does what they do--not because they are terrible people who can't be trusted to stand by you or them when it really matters.
You can find some truly good, reliable friends during your lifetime, but don't expect anyone to be perfectly loyal or dependable 24/7/365. No one's flawless, and even a good friend can change or let you down from time to time, either by accident or because other complications can get in the way, but (forgive me--Hallmark moment coming) that's part of what makes the best friends so great.
(Upon review, I realize that I've just reiterated a lot of things that others have already posted, but maybe that's a sign that there's some good stuff here. My apologies; I didn't intend to plagiarize.)
KimD, I agree with you and really like what you posted.
We cannot be too black and white and should never idealize anyone. I am cautious but not paranoid. I have made mistakes just like everybody else, sometimes ignored good advice and got into trouble, trusted wrong people, etc.
I have learnt that if I hear something negative about the one I want to be friends with, I must not believe it completely and jump to conclusions but if it's about "safety" issue, I will be extra careful. I try to get to know the person and decide for myself whether to trust the person or not.
A "warning" is different from empty gossip. It contains valuable information that will help one decide whether to trust that person or how to deal with them.