A difficulty not mentioned here in comprehension, specifically with movies and some types of songs in Spanish, or any foreign language, is cursing. Some teachers and schools shy away from this because it can be considered offensive or in poor taste. Yet not knowing these words can impede comprehension. I think a measured approach is best: as students, we need to know what these words mean, we've likely heard them in our native language, we don't necessarily need or want to USE them, but they can aid our comprehension of movies and songs, especially movies about crime where people use these words regularly, rap or other types of songs where the more cursing there is, the "cooler" it is. I have sought out teaching materials; one good one is called "Why our curses are the best," After Hours Spanish; the presenter is from Spain so obviously this won't help with regional Latin American curses but it's a great introduction.