Trader Joes house of shady deals

[Slick]

That's the game. Is your opponent trustable or not? If so, for how long? If you aren't comfortable, then you might consider not trading at all; but maybe everyone else is and you'll fall behind... Is the game using role playing? If so, read the empire's description. If no role playing, you could take your chances.

For absolute certainty, you could request that your opponent "gift" the items to you, and you will "gift" your stuff the next turn after examining the gift. I don't know a worse way to carry out a trade from the perspective of trust, though, nor many who would agree to this.

I'll say this: most of the regular players will not intentionally screw you on a trade. (Sometimes the game screws up diplomacy so make sure that it is the very last thing you do in a turn.) The trade may be better for them than for you, but most won't lie. They know that it'll be the last time they are ever trusted, and reputation is something that most players like to keep clean.