@NuclearSnail: You find a good voice teacher who understands registration and who is willing to explore the characteristics of your particular voice, and do the exercises that he or she recommends.
The core of the technique is isolating your chest voice and working with it until you understand what it feels like, then isolating your head voice and working with it until you understand what it feels like, and then learning how to blend them, and how different vowels and different sections of your range draw on them differently just by the nature of how vowels and voices work. This will also give you better control of your color and your intonation—chest voice is easy to tune, because it tends to be brighter (more overtones), but it tends to go flat, especially when you’re tired; head voice is harder to tune, because it’s darker (fewer overtones), and tends to go sharp.
But exactly what exercises will accomplish this in your case is really not something I can tell you here, without hearing you. This has a lot in common with personal training—a good personal trainer will look at your body type and the progress you’re making, and recommend changes to your workout routine that are tailored to you specifically. That’s why it’s important to have a good teacher.