Most instructors want students to not just memorize information, but be able to make connections and synthesize the material. Have high standards for your class and help the students reach them by trying various teaching techniques and exercises like active learning. Also, help your students prioritize the material. Perhaps you can provide a brief outline of objectives in the beginning of class. Office hours are a nice idea, but you look sort of scary.
Research indicates that students hesitate to talk to instructors, even when they want to.
One suggestion is to encourages students to e-mail. One-minute papers at the end of class are another way to get students to ask what they do not understand.