I've long ago figured out any "tells" that my close friends have, so they never get anything past me
When dealing with a stranger or someone who I don't know very well, I just look at the eyes. A good liar won't do some sort of eye-darting movement or avoid eye contact to make it obvious, but still, eyes almost always carry a message. If that message is at all different than what they're saying, then they're lying. At least, that is what I've found in my experience.
When I lie, I try to avoid doing anything that, if I was looking at myself, I'd recognize as a "tell". I act casual, using my usual banter and eye contact. I also try to keep them simple, so that for the duration of the lie I can actually somewhat believe what I'm saying.