Often times it is important to stop at the end of lecturing on a new concept ask who is not understanding. When I get a response, i will try to reteach the concept in a new way, or sometimes reteach the whole lesson, depending on the amount of feedback. It is not always effective to ask for those who have misunderstandings to admit their miscomprehensions before a class of their peers. To get around shyness or embarassment, I also try to allow students to tell me what they don't understand in their question of the day at the beginning of the day, in math journaling , math reflection, or after school or during resources in tutoring sessions of which I keep a log.
I use this feedback from my students to see where i need to reteach and how I need to reevaluate the way in which I am delivering my instruction. I try to find a way to clarify misunderstandings while keeping a focus on my instructional objectives.