I've been on a math kick this summer. Math Sense: The Look, Sound, and Feel of Effective Instruction by Christine Moynihan has been on of my favorite reads. It's a great foundational book about quality math instruction. It validated many of the strategies I've been learning for the past five years, challenged me to take them to a new level, and reminded me of some that I haven't incorporated as well as I would have hoped.
Here are just a few of the topics the author believes are important to the look, sound, and feel of a mathematics classroom. She addresses each one.
checking for understanding
identifying student misconceptions
setting and sharing lesson goals or objectives
using mathematical vocabulary
justifying and clarifying thinking
analyzing the thinking of others
and so many more
I would definitely recommend this book for any K-5 math teacher.