no idea, as to a teaching grammar; but just reading is a splendid guide. to wit,

“I remember once,” Cara told him, “who was it? Sister Modeste. She wrote on the board: What if they should never have united themselves in that, over there?" Cara had started to laugh, remembering the moment. "Panic! Se joindre, a homicidal verb. It's much simpler in Spanish. And then my friend Francesca, after the sister wrote out the answer, leaned across the aisle and whispered, 'Well, I'm certainly glad I know how to say that!'"

cool