Network, as has been said above, is one of the most important things you can do. Upload a lot of music: different styles, different emotions, game music (which is usually melodically driven) and film scores (which tend to be much more about creating a mood; although, you can still have strong thematic material).
Of course, one of the other important factors is that you have to be good. And, unless you're Mozart or Beethoven - and I can 100% guarantee you that you're not, because those kinds of composers come maybe once every few centuries, and if you were already that good then you wouldn't be here asking how you get hired - the way you're going to get better is by practicing. A LOT. Most of what you write, especially when you're just starting out, will be crap. When i started composing when I was 8 years old, 100% of what I wrote sucked. Nobody, besides my immediate family, has ever heard most of those compositions, even though I wrote a lot of them.
I'm not saying that to be mean, or to discourage you from working toward a goal. It's a fact that a lot of people seem to forget: all the contacts in the world (probably) won't help you get hired if your music sucks. And if you want that job, you're going to have to work for it: you're going to have to stretch yourself to try new things or learn new techniques, so every new track is better than your last (the worst thing you can do is plateau, and get into a habit of "Well, that piece was pretty good; let's keep writing like that").
Of course, what you can do to help yourself get better depends on what, specifically, you want to do. Do you want to score video games? Films? Become a singer-songwriter, or a songwriter for another act? Do you want to focus on orchestral, electronic, rock, 8-bit, or a combination of them? If you want to focus on orchestral soundtracks, then you're going to need to study a hefty amount of music theory: once you learn the 18th century 'rules' used in classical music, then you're allowed to start breaking them; it's one of the ways the Romantic composers pushed the scope of orchestral music in new directions.
I think I'm going to stop there before this becomes a 10,000 word rant.