Formal and informal communication channels have advantages and disadvantages for organizations. Formal channels include vertical, horizontal, and diagonal communication through official lines. They provide systematic information flow, clear authority, and coordination. However, formal channels are time-consuming, rigid, and expensive. Informal "grapevine" channels spread quickly but lack accuracy and responsibility. Effective communication uses a combination of oral, written, and nonverbal methods like speeches, reports, gestures, and expressions to convey messages.