[Windborne]

One easy way to get happy planets with alien races on them is to sneakilly ask for planets as gifts, returning the favor with a gift of resources to keep the stupid AI from realizing it has been conned by the deal.

Doing this late into the game with ones comptuter controlled allies can give you a planet every two turns if you do it right, then you only have to worry about the human players. Of course the new patch will hopefully have made the AI wise to this strategy, planets should NEVER be gifts, but if not we can all enjoy a laugh at the computers expense, and happy productive "gift" populations that become long standing parts of our empires well before we go to war with their former masters.