Alright, so this is obviously the last resort -- or maybe it's your first resort depending on how you want to handle the situation. Reporting your noisy neighbor to your landlord could yield some positive results for you. Your landlord may send them a letter or talk to them in person about the noise. Many apartment buildings have a noise clause in the lease and your landlord may bring this up to your noisy neighbor.
If things really get out of hand, you may need to call the police to get your neighbors to quiet down. You may not want to do this unless things are really bad though. If the music is a little too loud late at night, try banging on the wall before you dial 911. But if you hear yelling and fighting through the wall, and it sounds like more than just a disagreement, then a quick call to the police might be the best option for you, and for them.
Keep in mind that if you've exaggerated your noise complaint to the police, they come knocking back at your door and tell you not to call again. If all of these suggestions fail, it may be time to look for a different apartment or a new building. Good luck!