There is not that one magical thing that you can do to make your music louder... It's just something you learn during the process. The most crucial element is your mixdown. There should be no unnecessary peaks in your audio, because those will clip your limiter later on. After you get your mix clean, you can start boosting the volume on your masterchannel. My masterchannel typically looks like this: EQ (just some small touches and a highpass filter around 30Hz so you got more space to boost overall volume), then a multiband compressor to tame the dynamics and finally a maximizer, which is basically similar to a limiter