Principles of Language Learning
Language learning principles are generally sorted into three sub-groupings: Cognitive Principles, Affective Principals and Linguistic Principles.  Principles are seen as theory derived from research, to which teachers need to match classroom practices.  Here are some brief summaries of the principles that fall into each grouping:

Cognitive Principles
Automaticity: Subconcious processing of language with peripheral attention to language forms;
Meaningful Learning: This can be contrasted to Rote Learning, and is thought to lead to better long term retention;
Anticipation of Rewards: Learners are driven to act by the anticipation of rewards, tangible or intangible;
Intrinsic Motivation: The most potent learning "rewards" are intrinsically motivated within the learner;
Strategic Investment: The time and learning strategies learners invest into the language learning process.

Affective Principles
Language Ego: Learning a new language involves developing a new mode of thinking - a new language "ego";
Self-Confidence: Success in learning something can be equated to the belief in learners that they can learn it;
Risk-Taking: Taking risks and experimenting "beyond" what is certain creates better long-term retention;
Language-Culture Connection: Learning a language also involves learning about cultural values and thinking.

Linguistic Principles
Native Language Effect: A learner`s native language creates both facilitating and interfering effects on learning;
Interlanguage: At least some of the learner`s development in a new language can be seen as systematic;
Communicative Competence: Fluency and use are just as important as accuracy and usage - instruction needs to be aimed at organizational, pragmatic and strategic competence as well as psychomotor skills.

This is a very brief overview of various language learning principles, drawn heavily from H. Douglas Brown`s explanation (see resources for reference).  You may be able to come up with more or different interpretations yourself.  However you view language learning principles, these should form the basis or backdrop of the techniques you choose to use and the choices you make in the language learner classroom.