Expose students to more English. Encourage students to speak, listen, read and write English on a daily basis, not just while they are in class. Explain to students that part of language learning is seeing and hearing foreign words and sentence structures and making a mental connection between them and their meanings. Encourage students to join conversation groups or watch television and listen to the radio in English.
Practice concepts until all students understand them. Although it can be tempting to move on after several days on one subject, go slowly and break concepts down into their component parts. For example, teach question words, like "who," "what" and "where," and make sure everyone understands them before moving on to question sentence structure, punctuation and pitch. If some students seem to be holding others back, bring tutors into the class to work with students individually or pair successful students with struggling ones.
Review often. Complete formal and informal assessments after each major concept you teach to check what students do and do not know. If students score poorly on assessments, devote an entire class period or two to re-teaching the concept they are struggling with and test again. Devote a few minutes of each class period to review even when students score highly on assessments. Review not only what was recently learned, but also concepts from the earlier classes.