Work from clearly stated rationales, principles and objectives toward clear and measurable goals. The earlier a person learns a language the better. Learning a language before puberty from native speakers results in more authentic accents and better retention. Use the second language as much as possible in instruction. People who must use a language to survive or succeed, learn it more quickly and meaningfully.
Children learn languages more easily partly because they are less inhibited.
Do not inhibit them with too much correction and unnecessary information. Children all over the world have learned to understand and speak their language without formal classes. Learn from how children acquire their language skills. For example, children listen and speak before they read or write. Emphasize listening comprehension over speaking initially, then as the students are ready introduce reading and writing.