It will depend on what level of English they have already attained, as well as which language is their mother tongue. For example, if they speak an Asian language, you may have to start with the alphabet.
It also depends on the purpose for learning the language. If they need it for basic survival, you would want to focus more on conversation and basic reading vocabulary, possibly how to complete an application or a form.
If they really mean to learn it as a second language, then you will want to develop all areas of their language.
If they have basic English skills, you can build on those with theme-based lessons where the students read a text, learn related vocabulary, focus on a particular grammatical structure or two related to the theme of the text, and do some speaking and listening activities focused on the topics, using the grammatical structure and the vocabulary. Finally, they will need to write something using that vocabulary and structure.