I believe math is learned through communication, and much of that is talking. I try to make my class a place where students feel free to think out loud, ask questions, and respond to each other's thinking. Most of my instruction is exploration-based, and nearly all "practice" problems are done in teams of three at team whiteboards. (Thank you Building Thinking Classrooms!). I also have students work individually through concept-building exercises that we discuss at length as a whole class to ensure students understand the underlying "why". I use the "Concept Ladder" activities I've developed to help with this.