Can someone direct me to or guide me through some basic capitalization rules?

More specifically I'm having trouble with nationalities and races such as, I know the name of specific countries should be capped, like "Spanish," but what if it's referring to something less specific about that nationality like a fleet or something? Is it "Spanish fleet" or "Spanish Fleet"? Or if it includes a title, is it "Spanish Lord?"

Also, what about if it's a race as a whole like, "I hate humans." Should humans be capped? Or what about "Those dirty Martians stink" or "I'm an Elven princess" and "Oh no, the Humans are attacking!"

Any help is appreciated.