Many of us are taught from a young age to always tell the truth, regardless of our religious background or cultural inclinations. Telling the truth is almost universally regarded as a virtuos thing to do. However the argument can be made that in some circumstances it is unswise to tell the truth. In some cases it is even preferable to lie.
Well, to begin, to define what the truth is. Truth to me does not have to be objective, however from a subjective point of reference it must remain honest to oneself. If one is trying to be truthful he may not be factually correct. For example A man lets call him Bob is a studying physics for a test. His classmate Alice asks Bob for some help on a particular topic say Newton's second law. Bob has a crush on Alice, he tries to impress Alice by flexing his understanding of this topic. He confidently misinforms Alice before the exam, the formula was not FM = A. Both Alice and Bob get the question wrong in the exam. Bob had told the truth based on what his understanding of Newton's second law was, but Bob was still not being entirely truthful. This is because Bob wasnt being honest about his ignorance. He lied about his compotence to chance a positive perception from Alice. Suffice to say Bob had failed...
In most cases saying the truth is considered the correct thing to do. Lets say someone asks, "What work do you do?" at a social setting and you out of jest reply with "I am a doctor". Sure the result may be that people view you as sucessful and noble, but it completely falls flat when a man has a throbbing pain in his chest and falls to his knees and the entire party looks to you for assistance.
Even when you are saying a lie that you thought could never be found. Lets say your having trouble working as a Teacher and your colleague sits you down and asks if you if you are struggling. Its quite easy to reply dishonestly and say that you are fine, to remain courteous. Your colleague may never know what your feeling. However your students can pick up on the resentment. Your colleague may have had some useful insight as to how to deal with your problems. Lying made it not only your problem but the childrens problems too.
This doesnt mean there arent times that are acceptable to remain quiet or even lie. Lets say some evil man is on the hunt for your friend. Your friend was last seen with you. Suppose an individual runs up to you and with a machete and asks you where your friend went. He is explicitly saying that we wants to kill your buddy. Do you tell him where he is or do you say "I dont know". Do you lie to him, to potentially save his life? The answer is obvious, of course you save his life. In this world people are not perfect they are flawed in many respects. People have their unique circumstances sure, but in this situation the ethical thing is to make the judgement that you felt it was unsafe to tell the truth.
The effort should to always tell the truth, as much as possible. Even if it is painful to the recipient the truth is more valuable then the alternative. Let me explain, lets say there are two people. Carlos and Diana. Diana asks how do they look. Sure, one may initially simply respond that "they look good", to be kind and courteous. However its only best to say this when they actually look good, if someone asks its a question its important to discern exactly what the phatic meaning behind it is. If its a social statement made to elicit a specific response from you or if its a genuine question. Understanding the deeper meaning of the question and being honest to that question is still being honest. Lets say Diana asked Carlos because they were close and Diana valued the opinion of Carlos. Then it can be argued it isnt beneficial to lie. Sure there is a risk Carlos may upset Diana by telling her his honest opinion. He should still give his honest opinion. Take for example Carlos says this "Diana I think you look good, but that hat doesnt match with those shoes. Now I am not big into fashion and I am not in the know-how surrounding fashion. " Sure its much easier to lie and say "Yeah you look good". It may also be painful for Diana who may have spent hours selecting a hat and shoes that match to hear the truth, but the truth is more valuable and may allow her to see something from a different perspective. Potentially allowing her to come back looking even prettier.
All in all I can see that in nearly all cases its more acceptable to tell the truth then to lie. However there are cases such as when the safety of others is concerned. These cases are not clear cut and are definetly grey. I cant give a framework when is it okay to be untruthful. Id say a question one could ask themselves would be "Am I lying out of weakness or from a place of courage?" .