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?

An incomplete list of some individual factors

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: links between intelligence and aptitude in classrooms

Sex differences: English girls better at French than English boys

Level of first language (Cummins)

Empathy (Guiora)

—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

Dornyei, Z. (1994). Motivation and motivating in the foreign language classroom. Modern Language Journal, 78, 273-284.

Gardner, R. (1985), Social Psychology and Second Language Learning, Arnold, London

Skehan, P. (1989). Individual Differences in Second-Language Learning

Griffiths, R., and Sheen, R. (1992), ‘Disembedded figures in the landscape: a reappraisal of L2 research on Field Dependence/Independence’, Applied Linguistics, 13, 2, 133-147

Naiman, N, Fröhlich, M, Stern, H & Todesco, A 1978 The good language learner. Research in Education Series No. 7, The Ontario Institute for Studies in Education, Toronto. Reprinted Multilingual Matters, (1995)

Tremblay, P. F. & Gardner, R. C. (1995). Expanding the motivation construct in language learning. Modern Language Journal 79, 505-520.