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Use distractions and subterfuge.

Prepare a note for each player in advance and pass them out all at once. But all notes contain irrelevant stuff save for one. Examples:

 > Bilbo: The ring you found in the caves is cursed. You find yourself strangely fascinated by it. You decide it is better to keep this precious item hidden for now - don't tell the others about it.

> Gandalf: You observe a fascinating cloud formation in the sky. It looks like an oliphant.

> Thorin: Somewhere down in the caves you must have stepped in something unmentionable. It is stuck under your boot and is starting to smell.

Now everyone will be distracted with the message they got. And even if they suspect something, they can't know which one(s) of them that got an important message.

Similarly, to prevent players from getting "meta information" of you doing hidden dice rolls (to see if someone steps into a trap etc), you could do some dummy hidden dice rolls now and then and pretend to check something.