How do you learn quantum field theory? I took a tiny amount of QM in school - basically, solving the Schrodinger equation for a few simple systems. What's the next step?
If you're going to start learning QFT, I suggest you try to understand time-dependent perturbation theory as much as possible. Also, be sure you have a handle on special relativity and scattering theory. QFT that most people use is really those things combined.