Read and reread the Bitcoin white paper. As you read it, ask yourself questions like, "what if I do x, could I then double spend?" I've read it 3 times over the

Read and reread the Bitcoin white paper. As you read it, ask yourself questions like, "what if I do x, could I then double spend?" I've read it 3 times over the course of a year or two and it's always served as a good conceptual foundation.