Well, the question's pretty simple really. How do you show that your character is lying enough to not be accused of powerplaying, but not enough that the other people involved metagame?
I remember a recent bluff by the BHG got flamed severely when they claimed to have a very important hostage.
Basically, how do you RP a liar, or bluff, or... intentional misrepresentation of the facts?
I see two ways of doing this:
One. Make sure you got a real solid role-play reason for lying
Two. It's entirely possible to lie while appearing to tell the truth.
For example, if I am a junker smuggler, I could say I am taking cargo to a lawful base in system X, when in reality I am taking it to a unlawful base in the system.
They try to confirm this by looking at the player list, they will see that I am indeed in X system. Unless they catch me in the act (not happening if I avoid lanes), they won't know any different.
The lawful base in the region might not even be buying the cargo I am carrying and they won't know any different.
"Your men are located on Cali, in Tau-23. I'd suggest you pay me those credits, or they will not live to see another day. "
"Your men are located on Cali, in Tau-23. *The man clears his throat and looks at his feet before looking up* I'd suggest you pay me those credits, or... or... they will not live to see another day!"
What you can also do is make the lie obvious by stating false information.
ex: "We engaged the Outcast party 4 hours ago. Their Titans didn't stand a chance."
Well, see, there's the problem. The first sounds like a lie as my character might tell it. The second sounds like a panicked kid. The third sounds like a Xeno trying to sound tough.
The first lie is the most true to my character, but it's also indistinguishable from powerplaying from an OORP perspective.