It is a slow, peaceful journey and there is no silver bullet: practicing is the key for improvement.
I have a weekly class for music theory, which I enjoy a lot. What I seem to be a slow learner at is reading notes fast (treble and bass clef), and remembering the theory and logic behind the tones.
I don't practice much music theory outside the class. I consider building paper flashcards because music paper is quite specific.
What is your experience? What process or tool would you recommend to learn music theory?
PS: sorry if some words feel weird, music vocabulary is so different between French and English