The number one way to learn a new language is to speak it.
I remember when I learnt French in high school. The most effective teachers were the ones that forced us to speak it. Each week we would learn new vocabulary and phrases but she would then make us compose a conversation with a partner using all the words and phrases that we've learnt and stand in front of the class and perform our little sketch. I still remember my high school French phrases but because I haven't use it all at these past years, it's beginning to fade.