It depends on what role you play in the situation. If you have a responsibility to show loyalty to a person, not disclosing things they'd want to (or need to) know is pretty unfair. If you're constantly covering things up or not saying what you're thinking, the omission is as bad as lying because you're deceiving them.
My mother taught us never to lie, but rather to tell the truth creatively Each statement that comes out of your mouth must be a fact. Arrange the facts so that each one seems like a logical extension of the previous one; this way the less-than-desirable details can... fall away The trick is leaving gaps for the listener to fill in himself, while ensuring he doesn't realize the gaps are even there to begin with.
Each statement that comes out of your mouth must be a fact. Arrange the facts so that each one seems like a logical extension of the previous one; this way the less-than-desirable details can... fall away 
The trick is leaving gaps for the listener to fill in himself, while ensuring he doesn't realize the gaps are even there to begin with.