It's pretty much a given that when two PCs meet for the first time, they'll start sharing information. Often with no real in-game justification greater that "they look trustworthy". It's an obvious thing to do, under the basic assumption that you're working together so it's best to cooperate, and there's really nothing wrong with that.
On the other hand, some players like to deliberately hide information about their characters from their adventuring companions, and this can be interesting. If you've never done it before, consider having some snippet of personal detail about your character that they are reluctant to reveal - perhaps some family history, or some shameful event in their own past. Start with gentle steps like this.
But understand that the whole point of having secret information like this is dealing with the consequences of having it become known. If a secret remains secret for as long as your character is in the game, then it's not really relevant, and may as well not exist. (Having a secret may modify the character's behaviour, but that can be achieved with a simple character quirk, not necessarily requiring a deep, dark secret that is in danger of being divulged.)
In a dramatic sense, the reason for secrets is so they can be revealed. So while your character can fight against a secret becoming known, you as a player should be ready for the eventuality, and even look for ways in which the secret can be exposed, so that you can roleplay the results of the revelation. Spend some time consulting and working with your GM and conspire to have your secret be exposed at some point in a natural way within the campaign story.
A secret is a good roleplaying hook - but you need be unafraid to bait the hook and cast it into the open for it to really pay off.
Rejected title: Uncle Pete’s Ploys are Tragic
Commentary by memnarch (who has not seen the movie)
Ah, good. Finn's using the jacket for some shade from the sun. Also a valid question by Annie. Why do BB-8 and Rey trust each other? Well, they probably know of each other, or at least have semi-positive relations to the Resistance. Maybe. Also worth pointing out, Pete did another excellent job of answering a question that sounds like it's related to the one that was asked, but actually isn't. He's really going all in on keeping the "opposing players" out of the loop on what Rey knows.
I wondered about how BB-8 would actually travel with Rey from the wrecked AT-AT before, but I think the side net provides a good explanation here. They're just carried where the salvage was held when Rey came to town last time. I hope we get a funny image of BB stuck in the net at some point.
Diplomacy. Now that's a game I've never finished. I tried it once in college with my other housemates, but it ran very long and we had to stop when house guests needed to leave. I don't think anyone had fun with it at the end, so it never was picked up again in future game nights. There was definitely backstabbing involved, so it was slightly more fun than Monopoly in the sense of engagement, but it still had a hectic dragging-on feeling to it.
Commentary by Keybounce (who has not seen the movie)
I have played Diplomacy once. I didn't really understand the rules for contested moves. They told me it would make sense once I saw it in action. It didn't. I was relying on advice from the person that was helping me because I really didn't understand the game rules well enough. No, they did not have a simple first run so I could learn the mechanics and how things worked.
As I said, I played Diplomacy once. If they had treated me with a little respect, I'd have been willing to play with them more. As it was, it was a case of not understanding the rules, not understanding why I couldn't advance into a territory as expected, and then seeing some armies shipped halfway across the map while my friend advanced into my territory towards my production centers.
Now that I think about it, I never saw that person again. Diplomacy is not a game to risk friends over, it's not worth it.
This is interesting: Rey is saying she had no problem finding the ship, just trouble finding the modulator inside the ship. Which seems really odd. Wouldn't it have been in the socket where it belonged, so it would have been easy to find if she knew the ship? Being unable to find something that's where it belongs, and having to sell other scrap from the same ship while searching that ship for... all those marks is just not making sense to me.
Now, trusting other players is normally normal. But if there's PC vs PC, that trust can lead to... bad choices. :-)
Rey: Finding the modulator would have been easy, except for Tatooine’s sand messing up my scanner.
Rey: I had to do a gridded search. Took weeks longer than expected. I started selling other bits of the ship for food.
Finn: How do you two know you can trust each other and share information like this?
BB-8: We’re both PCs.
Finn: Would you trust Kylo Ren?
Rey: Corey’s my nephew. The uncle-nephew bond is naturally one of warranted trust.
BB-8: Like that time we played Diplomacy with your lawyer friends?
Rey: Our alliance was unstoppable! And you totally could have won if I hadn’t stabbed you in the back!