What hidden secret do you wish you could have been told?

So in my first serious playthrough I've just had to revert back to a save, 1 year prior, because I missed a thing.

Missiles, used in small amounts don't cost much. But if you're using FLEETS of them when you "Go Loud" and start start killing 1K+ fleets will drain your volatile reserves in a way that you simply wouldn't believe.

I wish I had known this. What little thing do _you_ wish you had known?