i've been testing the diplomacy aspects of the game....its easy to get ahead of ALL the civilizations in the beginning of the game if you have uber diplomacy. basically you just trade EVERYTHING to EVERYONE...either for cash or for other techs, or even scout ships if they have neither (if you cant get a weapon tek from a major get it from a minor that has weaker diplomacy). check every 2-3 rounds every race for a new tech, then buy it from them (with cash) then sell that tech to every other race including the minors...while your doing this research thru the trade/diplomacy techs (but never sell/give these away cuz they give you an edge in negotiations), then be the first to set up trade routes. eventually you'll see that you're ahead of the competition in techs especially once you get to the later government techs/trade techs. no one will go to war with you if you set up a trade route with each major race or at least most of em. anywayz i was able to beat 9 computer opponents on tough difficulty (all set to intelligent) with this tactic.
