-Building something on a moon then canceling it when you need some deut or when it almost finishes is good way of hiding fuel consumption when staging up ninjas.
-Espionage ships have cargo space.

-Sometimes the best place to raid is around your planet that hasn't been probed the longest. Most raiders scan every planet they pass through and take most of the profit. If you have not been probed there recently, then it is possible that nobody has sweeped there recently.
Mind suddenly became blank... Will think of something else to add later.
Any other tips you can think of?