Theories about how languages are learned can be complex. However, having some understanding of how people acquire and use languages can be useful to  teachers and teacher trainers in the field of adult ESL.

Second language acquisition theories address

• cognitive issues (how the brain processes information in general and language in particular),
• affective issues (how emotions factor into second language processing and learning), and
• linguistic issues (how learners interact with and internalize new language systems).

Here are 3 suggestions that instructors can use in the classroom and that teacher trainers can share in professional development sessions.

Meaningful interaction and natural communication in the target language(in this case English) are necessary for successful language acquisition.
Learners need to use the language, not simply talk about it. Give learners opportunities and purposes for communication that reflect or relate to their lives (for example role-playing a doctor/patient exchange).

Use authentic materials in activities whenever possible (like  listening for details in a recorded telephone message or reading classified ads from the local newspaper).

Effective language use involves an automatic processing of language.
To become proficient, learners need to move from a concentrated focus on grammar, forms, and structures to using language as a tool to accomplish communication tasks. Think about the purpose of each lesson (e.g., is it important that the learner produce a specific grammar point or communicate an idea?) and interject error correction only to serve those purposes. For example, if the activity is an oral substitution drill practicing the correct use of irregular past tense forms, it is appropriate to correct the verb form being used.

However, if the focus of the lesson is making small talk on the job-a communication that involves use of irregular past tense verbs-correction may simply consist of a repetition of the correct form by the teacher (e.g., "I go to a movie last Saturday" is corrected by, "Oh, you went to a movie. What movie did you see?").

People have affective filters (created by a variety of factors such as motivation, self-confidence, or anxiety) that can support or disrupt acquisition of a second language.
Create a classroom environment in which learners feel comfortable using and taking risks with English. Use activities that ask learners to work together or share information to build a sense of familiarity and community. Make sure the physical environment is as comfortable as possible. Avoid constant error correction and include activities that focus on overall ability to communicate meaning. Recycle topics or activities that motivate learners.