I was trying to figure out how best to set up my planet's specializations between manufacturing, research and economy. And it occured to me that the choices are already built into the game. Planets with moons get a 10% bonus on their production, so they would naturally be the best for manufacturing. Planets with rings get a 10% bonus for research so those should become research planets. And ones with neither would be well suited as economy planets. Of course some exceptions have to made in the event of special tiles, but overall it's an effective way of setting up your empire's economy.