I tend to favor radical honesty

Watch movies, read books and you'll find that a lot of problems and such are because people didn't just tell the truth.  Imagine, for example:

Jake: They asked me what they could offer you to get you to leave Home Tree and I told them the truth: nothing.  So they've decided to use force instead and they're coming here right now!

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Amy: I didn't fight Lucy Diamond and live to tell about it.  I had a minor standoff with her and then stupidly let her get away.  There was no fighting involved.

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Jack: Pitch lured me into a trap, captured babytooth, and kept me occupied until it was too late but there is some good news: I found out where he's keeping the little tooth fairies.  We can set them free.

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Romeo: Tybalt, you haven't heard about the wedding yet, but we're related now.  Kinsmen can't duel.  Sorry.

Juliet: Dad... I can't get married to Count Paris because I'm already married.  If you really want to disown me for marrying without your permission... I guess you have to, but don't disown me for not marrying Paris.  I can't.  It's illegal.

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Hamlet: The reason that I've been acting strangely is that I've been investigating my father's death.  There were indications it wasn't natural but I knew if people realized I suspected they'd try to hide all the evidence.  My uncle just confessed to killing my father.  That means he's not a king but a traitor.  I hereby banish him.

(The only reason Hamlet didn't kill him there and then, you'll recall, was that his uncle confessed to God and Hamlet didn't want to send his father's murderer on a one way trip to Heaven.  Banishment allows the uncle to become a sinner again.)

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Jack: Your father's blood, the blood that runs through your veins, is needed to lift the curse.  The fact that we know that and you don't is the only advantage we have over the ghost-pirate-things.  Whatever you do, don't let them know who you are.

[Next movie:]

Elizabeth: The reason I feel so bad is that I killed Jack and it turns out being a murderer comes with a lot of guilt.

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Simba: I exiled myself because the only reason Mufasa died was he had to save me after I was playing somewhere I shouldn't have been.  He had to run through a stampede to save me and that's how he died.  I've always felt that I was responsible for my father's death and I couldn't live at home with the shame of it.

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Brutus: In public everyone acts like they love you but in private a lot of people are worried that you're becoming a king.  If you don't back off on your ambition you'll lose the support of the people and there will be a revolution.  If there is one you know that I support the will of the people even over friendship.  So please, old friend, tone it down a bit.

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Tiresias: Remember the guy you killed at the crossroads when you were running away from Delphi?  That was the previous king.  Ask anyone and you'll find he was on the road to Delphi at the same time you were on the road from it.  The person who said there were two attackers instead of one was lying to make himself look less bad.  The good news is that if you go into self imposed exile now you should be able to have a happy life.  If you stick around trying to investigate further it will destroy you and your entire family and any chance Thebes has of knowing peace in the next three generations.

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Odysseus: Ok, crew, see this bag?  It's magic.  As long as it stays closed only favorable winds will blow and we'll be home in no time flat.

[Or if he didn't do that:]

Odysseus: I just learned that if we stop on the isle of the sun and eat the cattle there we'll all be killed.  So lets not do that.

Odysseus: Ok I've talked to the ghost of Tiresias and he says that if we avoid eating the cattle on the Island of the sun we'll be home very soon, but if we don't then we'll be shipwrecked and you'll all die while I'll have to be some god's sex toy for seven years.  So, seriously, let's not eat those cattle.

Odysseus: I have once again been told that if we eat the cattle of the sun you'll all die and I'll be a sex slave for seven years, so please let's all agree that no matter how hungry we get we don't eat those fucking cattle.

[For the record, if not for the crew eating the cattle of the sun, which Odysseus didn't warn them not to do until they were within hearing distance, Odysseus and the crew of his one remaining ship would have made it home safely before the suitors even invaded Odysseus' home.]

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Loki: If you kidnap my children and treat them all like shit I'm totes going to turn on you and bring about the end of the world so DON'T KIDNAP MY FUCKING CHILDREN!  Seriously, what the hell are you thinking?  How many times have I saved your lives?

[Ok, Loki probably didn't see that one coming, but at some point someone should have mentioned that maybe pissing off the god who has allies on both sides of the eternal conflict and an ability to pull off anything is not the best idea.  Plus Loki is the mother of Odin's horse so Odin has to wonder if maybe some time when he rides into battle the horse will come to a dead stop, send him flying to land flat on his face, and then abandon him on account of what Odin did to the horse's siblings.]

The Aesir: Hi really nice wolf who we've kidnapped and raised.  Even though you've always been so nice to us we're kind of afraid of you because you just get bigger and bigger and bigger and never stop growing and your size is scary.  Do you think you could maybe go on a diet?  Please.  *puppy dog eyes*  For us?

[At the very least it's better than skipping straight to: let's lie to him, involuntarily restrain him, and make sure he'll be our mortal enemy until the end of time.]

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Edward: I promised I'd tell you the truth, so here it is: I'm not actually human.  I'm a nigh immortal hemophagic being who is trapped in the form of a 17 year old since that's when I made the transition from human to this species.  It's why I'm so cold and my eyes aren't a consistent color.  I'll tell you more when we have more time but for now the two important things are these: First, the blood I drink isn't human.  I'm no more a threat to ordinary people than someone who eats steak.  Second, for reasons that are so complex I can't get into them now, but I will absolutely fill you in on when we have time, it is vitally important that the fact I'm different from the human students be kept secret.

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Roger Ferris: I promised I would never lie to you, but I've been ordered not to tell you the truth about what I know about him.  I begged to be allowed to tell you the truth, but the orders still stand.  So please don't ask me about him.

[The worst part of that movie though was the treatment of Omar Sadiki.  It's not that they used him without his knowledge which would be bad enough, it's that they set him up in a position where he'd be in mortal danger and then didn't bother to protect him.  There is no legitimate reason that Sadiki should have died in the movie.]

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Flynn: I didn't steal the crown alone and I just saw my two partners on the shore.  They've tracked me down and if I don't give the crown back to them they might do some very bad things.

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Cinderella: Would you still be attracted to me if I were a serving girl working in the dirt all day?  Because I am.  I'm only allowed to keep these clothes until midnight.

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Tony: Pepper, I'm dying.  That's why I'm giving away so much of my stuff.  That's what I'm reviving the expo.  When I'm gone I want to have had some kind of positive legacy.  Which means I also want the company in good hands.  That's why I'm giving it to you.  You've always been better at that sort of thing than me anyway.

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Nick: You've been frozen for decades.  We considered making a fake hospital room that resembled your time and easing you into the present day but we decided that just telling you the truth was better.

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[Different movie:]

Nick: Shield answers to a council which is short sighted and likes the idea of bigger and more devastating weapons, so we've been ordered to create weapons of mass destruction but I personally believe that our problems can be solved without resorting to mass murder and if you all can work together to stop Loki and his coming army it will prove that we don't need these weapons, we need teams of people who can distinguish between the enemy and the innocent in a way no nuclear bomb ever will.

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Obi-Wan: Your father didn't die, as such.  His soul was destroyed.  You must always beware the Dark Side because even if you turn to it with the best of intentions it will destroy all of the goodness within you until there's nothing left but a an evil husk that used to be you.  That's what happened to your father.  Darth Vader was once your father, but now there's nothing of your father left but a few memories and his DNA.

[Ok, it's not true, but Obi-Wan thinks it is.]

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Yoda: I'm Yoda, but before I train you I want to get to know you first.  Would you come to my house for tea?

[But in Yoda speak.  "Come to my house for tea, will you?" and whatnot.]

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Yoda: I don't think you're ready, and if I'm right then going to face Vader will turn you to the dark side which would mean that YOU would end up a tool of the Emperor working against everything your friends have fought and suffered for.

[But in Yoda speak.]

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JT: I'm related to a big time criminal.  He won't talk to me, but I bet he would set you up with a job.  You might have heard of him: Jack Schmidt.

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Inara: I want to stay, but more than that I want you to want me to stay.  So do you want me to stay?  Because if not I'm leaving.

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Westley: *Takes off mask* Hi, Buttercup.  I've been trying to get money for marriage by working on a pirate ship but I'm somewhat concerned about the fact that you've become engaged since I sailed away.

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Red Queen: If you turn off the security systems it'll release monsters.  Don't believe me?  Look at this security footage.

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And so on.