Scout, of Friction Powered Information Exchange, has compiled a list of things to look out for in potential friends and lovers. Pay attention to this--it could save your life!
Don't trust a man* who uses false charm and flattery to get what he wants.
Don't trust a man who tries too hard to impress others.
Don't trust a man who ridicules or is cruel to others for his own entertainment.
Don't trust a man who disrespects his parents (or elders).
Don't trust a man who has no qualms about gaining at someone else's expense.
Don't trust a man who never sacrifices for the benefit of others.
Don't trust a man who always blames someone or something else for his own shortcomings and never admits that he is wrong.
Don't trust a man who uses others' weaknesses to manipulate them.
If a man has proven himself to be a liar in trivial matters, don't trust him to be honest in anything else.
Trust your own instincts. Don't write off abnormalities in behavior as harmless eccentricities or idiosyncracies.
*All of the above apply to both men and women. Substitute woman, she, or her where necessary.
Any one of these should be a HUGE red flag.