When you find them saying something or acting a certain way around certain people but when other people come around its like a completely different person.

you can't always tell at first. I found out that with friendship. some people will be sincere at first and then once you get to know them they let their guard down and the real them shows.. they tell you one thing one time and the next time, it's something different or in the case of my "so called friends" it's "I will always be here for you if you need me' but then when I am sick or having a bad day and I need them they don't know who I am but if they need something then I am their best buddy. It doesn't take much to learn. It may take a while but you will learn.

1. Aliens often wear huge sunglasses to hide their eyes. Most aliens have large, staring eyes that are hard to conceal. Sunglasses help them appear more normal. 2. Aliens have cold and clammy skin. Many aliens wear synthetic skin in order to pass themselves off as human. It's never as warm as real skin, and it often feels "slimy" to the touchy. 3. They smell. Aliens use all manner of deodorants, perfumes, or lotions to disguise their natural scent, which is offensive to humans. 4. Aliens are obsessed with technology. They spend hours chatting on cell phones and sending e-mails. But they're not conversing with people -- they're actually transmitting data they've accumulated back to their home worlds. 5. Aliens have strange bodily proportions. The newest breeds of aliens attempt to imitate human appearance -- but they never quite get it right. They are like exaggerated ideas of human perfection. Their stomachs are too flat, their chests too big, their faces wrinkle-free. 6. Aliens have strange diets. Aliens may not be able to digest most human foods. Because of this, they are limited in the types of foods they can eat, and they may become vegetarians. Watch out for people who eat a lot of melons -- that's an alien favorite. 7. Aliens dance in inhuman ways. Most alien species have a completely different physiology than ours. They have the ability to move their bodies to music in a way no ordinary human can, and this results in a dancing style that is quite breathtaking. 8. Aliens do not understand Earth's sense of humour. Forget what you saw on Mork and Mindy. Aliens find it difficult to understand laughter -- even a simple knock-knock joke can throw them completely off. They might laugh at inappropriate times -- like during a funeral -- or stare blankly at the funniest jokes. 9. Aliens dress in oddly revealing clothes. Aliens find clothing irritates their flesh, so the less of it they wear, the more comfortable they are. They also like to keep their fake human skin exposed to air, to allow it to breathe.

Ask them a deep question about politics open ended that you know should have only one good answer.

catch them telling lies

If the person makes up big lies to impress you then you know their phony.

What's the meaning of phony???

If you are getting an inkling that they are fake...they probably are...but, bear in mind most people put up fronts to protect themselves until they are comfortable with you.