I've seen it used very successfully with students from primary grades to adults in a large lecture hall. You can also use it for vocabulary or concept development, comparison-contrast activities, sharing parts of homework, summaries, inferences, problem-solving, etc.
This particular description is from Jeffery Zwiers (Building Reading Comprehenison Grades 6-12, 2005) but you can find it described in lots of different places.
1. Create a question or prompt that will get students to use their background knowledge, etc., and ask the to think of an answer for about 20-30 seconds, then write (quickwrite) an answer on a piece of paper. This should take 2-3 minutes, tops.
2. Then have students work in paris. One person shares at a time--each partner should listen politely, show interest in his/her partner's thinking (I actually model what this should look like--eye contact, nodding assent, etc.), and ask clarifying questions if needed (this should also be modeled). The partner talking needs to give support for his/her ideas (evidence from the book, background knowledge, experience, discussion, etc.). The time should be limited as well.
3. Once both partners have shared, then they turn to another pair and share. Instead of sharing his/her own ideas, each partner should share what his/her partner said instead.
Other variations could be Think-Pair-Write-share, Read-Pair-Share, etc.