I hate when people overuse:
"Can you do me a favor"? The more someone uses this expression the less likely they are to help you when you need a "favor". Just say, can you help me out; you never intend to repay the "favor".
When someone needs something but because your closest your expected to get it for them. When you say no they make it out like your inconviencing them.
I find that the type of person that over uses both of these or use them in conjunction are manipulative selfish aholes.