Listening to a lot of background music of different styles can be really helpful. One source of good background music to take examples from would be, in my opinion, World of Warcraft. Because the game does a really good job of incorporating emotion into their background music. And a lot of it is phenomenal. So the first thing you must do is compose it to fit into the scenario or location it would be playing in.
Take the humans, for example. In WoW, they're portrayed as the good in the game. They're very chivalrous, and act courageous and with much dignity. They're very powerful and very much in a crusade sense to bring right to the world.
Here is the background music to their big city:
StormwindNow, let's visit the opposite side of the spectrum. The orcs. A very brash and brute race. They're seen as barbarians. They lavish in battle and bath in the blood of their enemies. You probably get the idea.
Here is the background music to their big city:
OrgrimmarAs you can tell, it's very important to understand just how much of an impact music can have in any movie, show, and videogame. Even silence plays a big role. Just take some time to sort of study the background music in games, in movies, etc. Listen to how the composer uses the instruments so create suspension, energy and calm. Perhaps you already knew to be doing all of this, but this makes up a large chunk of background music.