Officers and Mayors

it's better to have your officers specializing in one thing using them for different things requires a lot of thought:

Mayor:
High Politics: Increases production output and shortens time of construction in your city.

High Military: Shortens your troops training time, and your attack power increases.

High Knowledge: Decreases the time taken to research and the time to build your city defenses and your defense in that city.

When sending attacks:

High Politics: Pointless

High Military: Stronger attack power - Good for planes, rockets, navy and all out attacking in general.

High Knowledge: High defense power/armor - If your army mainly relies on tanks, such as if you send out 10k H Tanks to take the hits whilst you use 10k Rockets so that the rockets do not die.

Fields:
Garrison 1 officer with high politics and only dispatch with 1 scout, otherwise food output for troops in fields is 2x than when they are in your city. Minimum troops in field means maximum output. Scouts are also real quick.