Start by reading my favorite non-fiction book, The Gift of Fear by Gavin DeBecker. He gives a lot of good information on what kind of people aren't trustworthy and how to spot them before they hurt you.
After explaining that most danger happens when we ignore our own best instincts, DeBecker's first warning is to watch out for people who won't take "No" for an answer. People who try to step over our boundaries, who won't listen when we don't want something, or we don't want to do something. He gives some good examples to clarify this. Read the book.
My own comment on this is that many people, particularly young women, think that trust is a sort of gift you hand out to someone because you like that person a lot, or you have fallen for that person. The truth is, trust has to be earned and earned over a significant period of time.
Half truths, lies, and changing patterns, behavior, and ignoring you. Your instincts are the best indicator but, if you can't trust them then observe and listen more carefully.
they wud be ariund u aal the time,call u again nd again and always talk of things they r interested in and wud lie constantly......they might delay any of ur work by their stupid lie-" i forgot it" .....happened wid be last year itself
They have an evil aire about them. They are very inconsiderate and don't keep their promises. They don't look in your eyes most of the time, but really good liars can look in your eyes while they stab you in the back....
Can't make eye contact!
Well, if they keep trying to get close to you and slide their hand in your pocket....that's one way to tell.
If you've just met them and they ask you for money....that's another. If they call you on the phone and they tell you that you've won a fabulous prize....that's another....if they say they just want one little bite of your dessert and then they keep digging in....that's another. Sometimes they will even have bumper stickers warning you ....doormats.....signs on their gates....tattoos on their foreheads....all sorts of warnings.