Speak English at home. This is the biggest, easiest mistake to make. You go about your day, you're on the job working partly in English, you go to your English class, and then you go home and revert back to your native tongue. While you may be making slow improvements, you'll never get past that dreaded lingual plateau. Make a point to speak it at home, too. Have only English at the dinner table. Stick to English TV at home. Make it as 24/7 as possible.