I have always tried to make a point to never waste any time in the classroom-my time or my students' time. Everything we do is at a fast pace with quick transitions (hopefully:). Some of this is because it's just my personality and it is partially because there is so much to do over the course of a day and curriculum to teach in a year.
One strategy I've used to help make my instruction more efficient is to give pretests before my math units. This allows me to see if there are areas that we can work quickly through or areas where I may need to schedule extra time. I also use the pretests to organize my groups for our math workshop. One of my favorite pretests is my addition and subtraction pretest. It's very basic, but I love how easy it is for me to determine exactly where my students are with addition and subtraction. I've organized the questions by level of difficulty, starting with 1-digit plus 1-digit and then progressing to more and more challenging problems, and I've used a similar strategy with the subtraction pretest. You can click on the picture for a FREE copy.