The Lexis approach to learning a foreign language stresses learning fixed "chunks" of language -- each called a lexis -- that include familiar phrases as well as forms that have only a few variations. This includes common phrases like "I'm sorry," "Wait up" and "Thank you" that are frequently used but not completely logical. It also includes phrases that have only a few forms like: "I am ___ hurt" where the blank is usually filled in from a standard list that includes words like "really," "quite," "not" and "very."
Sandwiching is a technique to help students learn -- and understand with a minimum of explanation -- phrases in a foreign language. If L2 is a phrase to be learned, and L1 is the translation of L2 into a known language, the instructor says L2-L1-L2 and expects the student to respond with L2. In a Spanish class for English speakers, the instructor would say: "El gato esta en la mesa. The cat is on the table. El gato esta en la mesa." The student would answer back: "El gato esta en la mesa." All the grammar is heard but not explained, and the student knows what the sentence means.
Back chaining is a linguistic technique that is especially valuable in learning languages that tend to pile on prefixes and suffixes to produce long words -- like German, Russian and Turkish. The instructor teaches a long word by first saying the last syllable -- which the student repeats. Then the instructor says the last two syllables -- which the student repeats. This continues until the student can say the whole word.
Total immersion -- the student speaks only the language he is learning -- is generally considered the best path to fluency. This ideal is obviously impossible to use early in the process if the student is going to be doing any speaking. A variation on total immersion that can speed up to process of gaining fluency is called "code switching." This technique allows the learner to use native language words or even short phrases to fill in when the words or concepts are unknown in the language that is being learned.