-When another tribe asks to trade something with them, they will often try cheating you. Instead of accepting right away, propose a counter offer. Once the counter offer screen appears, click the items they are offering so that the "What will you give me for this?" option appears, then click it. They will now offer a list of things that often were not listed in the initial trade.
-If you are at war with another nation, to trade for everything they have, type in as many 9s as you can in the money received per turn. They will offer to trade anything they have for one of your territory maps (or anything else.)