Aptitude:
Why do you think some people are good at learning other languages?
Do you think the same people learn a language well in the classroom as learn in a natural setting, or do these demand different qualities?

Age:
What do you think is the best age for learning a new language? Why?
How would your teaching of, say, the present tense, differ according to whether you were teaching children or adults?

Other individual factors:
Do you think that girls are better than boys at second language learning?
What personality would be best in the language classroom?

Aptitude

— most aptitude tests predict success in L2 academic classrooms

—aptitude breaks down into different factors such as memory and grammatical sensitivity

Cognitive style: a person's typical ways of thinking, seen as a continuum between field-dependent (FD) cognitive style in which thinking relates to context and field-independent (FI) style in which it is independent of context

Extrovert and introvert: people’s personalities vary between those who relate to objects outside themselves (extroverts) and those who relate to the contents of their own minds (introverts)

Intelligence: between intelligence and aptitude in classrooms

Sex differences: English girls better at French than English boys

Level of first language (Cummins)

Empathy (Guiora)

Motivation and L2 learning

— both integrative and instrumental motivations may lead to success, but
lack of either causes problems

— motivation in this sense has great inertia

— short-term motivation towards the day-to-day activities in the classroom
and general motivations for classroom learning are also important

Links: Attitudes Motivation in SLA Motivation Test