Drills and other exercises

When it comes to achieving oral active fluency (speak naturally), drills are a must. As I undestand it, they have been used extensively for the first time during WWII when the Americans had to teach Japanese and German to thousands of soldiers in a quick and efficient way while there were not that many Japanese and Germans who wanted to teach them. So they developped effiency minded tapes that the soldiers could use without assistance. These tapes contained drills of various types that you can still use with good success :

Substitution drills : Such drills aim to have you master some syntaxic patterns (phrase types) without having to think. For example they will say "Jose va a comprar un coche mañana" and then give you a word to substitute in the phrase, making all the necessary changes. For example they say Nosotros and you answer Nosotros vamos a comprar un coche mañana, and then agacuates, where you answer Nosotros vamos a comprar agacuates mañana, then ayer and you answer Nostoros hemos comprado aguacates ayer, and so on. Depending on what they make you substitute, such drills can be called tense, persons, number or construction subsitution drills.